Since a couple of months I have had the pleasure of working on a Google Web Toolkit (GWT) project. Google have produced a range of quite well integrated tools for it an it is quite a smooth experience, even on an embedded platform such as the one I am working with.
Unfortunatelly, it seems that the Google Plugin for Eclipse (GPE) relies heavily on the users local Temp folder in windows, and generates quite a lot of files to it. After a couple of months, first eclipse, then MinGW, simply wouldn't start. Or sometimes i took hours to get it working. It turns out that you can't have too many files and folders in a folder, and there is no mechanism in Windows (that I know of) to automatically clean out the Temp folder or even give a warning when it becomes full. If the Temp folder gets full, it prevents some programs from operating correctly.
Solution: Delete the content of the Temp folder ("C:\Users\'your user name'\Appdata\Local\Temp" in Windows 7). It's as simple as that.... and it worked like a charm for me.