Rather than switching off with the button, try
holding Down "alt +sysreq" then, while holding
those down, slowly type "reisub". This is a safer way to
reboot your machine than holding down the power
button. You can look that command up in wikipedia
or on this list for more info on how it works. Then if
it doesn't work, at that point you go to the button push.
The reisub method provides a way (usually) to reboot a
Locked machine w/o damaging any system files
on the drive.

As far as your problem goes, did you do the
md5checksum on the disk before installation?
(that is assuming it was a disk install and not
Just an in-place instal). If you don't have too
much time invested into the new system yet
It could be worth it to try reinstalation in
Case something went wrong there. But
it would probably be smarter to wait a bit
and see what some more of the people
around here that are a lot more in the
know than me have to say.