Yes, I am getting this too, way too often the last day or so. I restart and it still comes back. This was happening to me both at home and at the office 2-3 months back after installing myeclipse in both places. I believe that it is related to the problem that many people are/were having when backspacing in a jsp and receiving error messages and having to restart because everything done after that would not be saved. My problems went away for a couple of months (I didn’t reinstall or update anything), now they have come back with a vengeance the last couple of days (again, no updates or reinstalls). It’s a know problem. See here:
http://www.myeclipseide.com/PNphpBB2+file-viewtopic-t-6613-highlight-backspace+error.html
There is a workaround suggested there – which I am about to try – as well as option to install 4.01M1 if you have a compatible version of everything else installed and want to give it a try.