Eclipse suddenly started to do weird things

[Titeuf49]

First of all, sorry for my bad english. I'm new on android but i can resolve some kind of logcat problems like classnotfoundexception ecc.But that one, i really can't understand it.Since a while, eclipse started to do really weird things. First, when i try to open it, it pops out a window saying "This Android SDK requires Android Developer Toolkit 21.1.0 or above. Current version is 21.0.1.2012-12-6-2-58. Please update ADT to the latest version". So i click "Check for Updates" and after a while it appaers another windows where is written "no updates were found". Oh cool it asks me to update and he can't find updates.But anyway: after i close it, it immediately appaers to me this error on the error log: "Unhandled event loop execution". I double click it and it appears that:\[code\]java.lang.NullPointerException at com.android.ide.eclipse.adt.internal.wizards.newxmlfile.NewXmlFileCreationPage.updateAvailableTypes(NewXmlFileCreationPage.java:1062) at com.android.ide.eclipse.adt.internal.wizards.newxmlfile.NewXmlFileCreationPage.createControl(NewXmlFileCreationPage.java:536) at org.eclipse.jface.wizard.Wizard.createPageControls(Wizard.java:174) at org.eclipse.jface.wizard.WizardDialog.createPageControls(WizardDialog.java:736) at org.eclipse.jface.wizard.WizardDialog.createContents(WizardDialog.java:608) at org.eclipse.jface.window.Window.create(Window.java:431) at org.eclipse.jface.dialogs.Dialog.create(Dialog.java:1089) at org.eclipse.ui.internal.actions.NewWizardShortcutAction.run(NewWizardShortcutAction.java:122) at org.eclipse.jface.action.Action.runWithEvent(Action.java:498) at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584) at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501) at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411) at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053) at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4169) at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3758) at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2701) at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2665) at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2499) at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:679) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:668) at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149) at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124) at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629) at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584) at org.eclipse.equinox.launcher.Main.run(Main.java:1438) at org.eclipse.equinox.launcher.Main.main(Main.java:1414)\[/code\]Session data:\[code\]eclipse.buildId=v21.0.1-543035java.version=1.7.0_10java.vendor=Oracle CorporationBootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=it_ITFramework arguments: -product com.android.ide.eclipse.adt.package.productCommand-line arguments: -os win32 -ws win32 -arch x86_64 -product com.android.ide.eclipse.adt.package.productThis is a continuation of log file C:/XXXXXCreated Time: 2013-03-23 14:54:10.477\[/code\]I don't know what that means but looks like that's not a project's code fault himself.Also, that first time it happened that problem, i opened the SDK manager i saw all my before downloaded files wasn't installed anymore. After i reinstalled 'em, anyway, sometimes (but for some strange reason not all the times) some sdk installed needs update (even if i updated 'em one or two days before).But now the big problem: all my project classes reports errors: they doesn't recognize things like floatmath or opengl es matrix etc (but even silly things like a class name); and if i check classes where it looks like there aren't errors (by the image of the class in the package explorer, where it usually pop out a red cross on the left of the name of the class), there are anyway errors and even really silly (like: @Override cannot be resolved to a type... what?!). That's not my fault: i launched all my project several times before that annoying problem popped out and they worked absolutely fine, uh.And a last thing: when i save something on an xml file (uh another problem: the main in the layout folder disappared...), it appaers that:"'Running Android Lint' has encountered a problem. Failed". I click on details and it shows "Failedjava.lang.NullPointerException". If i check on the error log, it shows to me that: "failed". If i double click it, if shows me that:\[code\]java.lang.NullPointerException at com.android.ide.eclipse.adt.internal.lint.EclipseLintClient.getTargets(EclipseLintClient.java:890) at com.android.tools.lint.client.api.LintClient.getHighestKnownApiLevel(LintClient.java:609) at com.android.tools.lint.client.api.LintDriver$LintClientWrapper.getHighestKnownApiLevel(LintDriver.java:1751) at com.android.tools.lint.checks.ManifestOrderDetector.visitElement(ManifestOrderDetector.java:396) at com.android.tools.lint.client.api.XmlVisitor.visitElement(XmlVisitor.java:170) at com.android.tools.lint.client.api.XmlVisitor.visitElement(XmlVisitor.java:209) at com.android.tools.lint.client.api.XmlVisitor.visitFile(XmlVisitor.java:150) at com.android.tools.lint.client.api.LintDriver.runFileDetectors(LintDriver.java:806) at com.android.tools.lint.client.api.LintDriver.checkProject(LintDriver.java:732) at com.android.tools.lint.client.api.LintDriver.analyze(LintDriver.java:340) at com.android.ide.eclipse.adt.internal.lint.LintJob.run(LintJob.java:153) at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)\[/code\]Session data:\[code\]Framework arguments: -product com.android.ide.eclipse.adt.package.productCommand-line arguments: -os win32 -ws win32 -arch x86_64 -product com.android.ide.eclipse.adt.package.productFramework arguments: -product com.android.ide.eclipse.adt.package.productCommand-line arguments: -os win32 -ws win32 -arch x86_64 -product com.android.ide.eclipse.adt.package.product\[/code\]So what's the problem? I tried in the way written here When I load ADT why do I receive the error "The Android SDK requires Android Developer Toolkit version XX.X.X or above?" , but after that the android XML disappared like magic.So can anyone help me? Many tanks in advance. Regards