I just corrected a really strange and infuriating issue with the trackpad on my Acer Aspire One running Ubuntu Intrepid. I'm going to write the whole story in case someone finds it useful, but here is the short version: trackpad quit working and didn't come back with a reboot. The solution was to hit Fn+F7 a couple of times (didn't work on first press, but did after a few presses...).
Now for the long version:
My fancy new Aspire One went to sleep (suspend) on accident--I know there are some unresolved issues with devices after suspending, so I've tried to avoid it--and I couldn't make it wake up, so I did a hard reset by holding the power button down for ~5 seconds. However, upon reboot, I was horrified to find that my trackpad no longer worked. It still showed up in the hardware profiler and in the kernel boot log, but it was totally unresponsive. No cursor movement, no clicks, no nothing. I rebooted. Still nothing!
I scoured the intarwebs looking for a software solution, including purging/reinstalling the xorg drivers, reloading modules, etc. to no avail. However, I did find a forum post where another Acer user had reported a nonfunctional trackpad that followed him across several Live CDs, suggesting a hardware issue. I was horrified by this prospect, as I love my little machine and I've finally gotten it configured to my satisfaction. Luckily, this user was kind enough to post his deceivingly simple solution: re-enable the trackpad using a key combination of Fn+F7.
I don't remember ever pressing this key combo to disable it in the first place, so I'm forced to assume that it happened on its own. Now I know how to fix it, should it happen again.