I have same problem. Touchscreen won't respond, or responds sporadically, etc. Sent the N900 in to Nokia for warranty repairs. It came back working. I restored my previous settings from a backup, and now the touchscreen is working poorly or not at all. I can ssh into the phone, and have been un-installing apps to try to find the bad one. No luck so far. Any ideas on how to trouble shoot via ssh/root access are welcome.