I am using Helios on Mac Snow Leopard. I don\'t know why but all of a sudden my arrow keys and delete button start not working only on Eclipse (so Eclipse ignores them) but
I have encountered this problem for years. It happens so infrequently however, that I almost always forget what I did to solve it. Restarting fixes it most of the time i think, and a few times "refreshing" worked, but nothing works 100% of the time.
In any case, someone on the bug report suggested just putting MacBook in Sleep cycle. This worked like a charm for me, so putting it out there for future reference.
https://bugs.eclipse.org/bugs/show_bug.cgi?id=344290#c24
Incidentally, I have experienced similar behavior with other applications, in particular Firefox. My thought is that it has to do with key bindings in general, and any application that provides overrides for defaults in the OS (this is a pretty huge assumption, so take with a correspondingly large grain of salt). I have also had this happen to me in Xcode, but a simple restart of the application fixes, whereas with Eclipse that wasn't sufficient most of the time.