Sorry to hear about your problem, but this solution shouldn't interfere with the touchscreen at all, I have been testing this for days and haven't had any issues, I'm using stock kernel, so if you're using something different, although unlikely, it might be the problem.

As for a possible solution to your situation, at first, when I was experimenting with several approaches I lost touch input several times, and my WiFi connection was also set to "Always ask" and bluetooth off or useless..., workaround? press Ctrl-Shift-x on your N900 and you should get a terminal, revert to your old driver and try to find out what might be wrong...

Now, if you did the changes manually and the evdev_drv.so file was named differently, your keyboard might not work either, in this case the only solution I know is to reflash rootfs, if someone knows how to get access to rootfs on a device in this condition (or even better, when it waiting to be flashed) it would be great to know.

Perhaps you could try putting it in R&D mode, it does some wonders from time to time with its "oh so cool" black magic.