Hello, I don't know if this helps you, but I just had a simillar problem.
Lyx worked perfectly (including hebrew) until I played with my XFree86. I tried to upgrade my XFree86 from RedHat rpm's for their new beta. As a result, I also couldn't type the same letter twice. This happened in english (I didn't test the hebrew). However, this also effected other things (outside Lyx) such as not being able to doubleclick twice in a row. In my case this was solved by going to the original XFree86 which came with Redhat-7.3 (the one I'm using now). The problem reappeared once when I played with the NTP (network time protocol) on my system (I don't know if this is related), but returning this to its original state and restarting X, solved my problems (for now). Hope this helps, Amir
