Today I see a strange behaviour of Eclipse 3.5.2 for the first time in 3 months.

First, when I run a main function, it runs a previously compiled version. Let's say I press Ctrl+F11 in the window with an open java class and existing main function. Usually it rebuilds the class and runs a new version. Today even if there was a compile mistake, it would run fine. So I guess it does not recompile the class.

Next, more strangely, if I intentionally make a mistake in the code and Eclipse underlines those lines in red, still the project Explorer does not mark them as containing errors. They remain of grey color if there were not any errors.

First I did not know how to solve this problem. I tried to reopen the project, restart Eclipse and finally reboot the OS. After the tenth attempt, after rebooting, Eclipse said that all project's files are "OUT OF SYNC with the file system". When I pressed "Refresh" - F5 on a project's header name in Project Explorer it finally marked all the files with errors as containing errors and running the main function gave the desired result.

An hour of my work passed and this happened again , with the other project. All the same. No marking of files as red, running no matter what old version of class with no compile errors.

And since Eclipse does not tell that files are out of sync, simply pressing F5 on a project cannot help.

What can you suggest?