are you overclocking? if you are, downclock to 1GHZ; you're not stable.
do you have any apps that are behaving badly on 4.0.4? if so, wipe, do not restore apps, observe for 24 hours. if good, then restore one by one until you find the culprit.
have you done a complete wipe? see above.
are you using the latest proper gapps?
this particular build has been tested for 2-3 days straight. no issues at all with any of the testers (aside from what has already been there).
pershoot,
I too am having similar issues and can't seem to track it down to an app. I get random crashes, sometimes it will crash while just sitting there. I did do a complete wipe and reinstall of all apps,etc.
I used the following files:
gapps-ics-20120317-signed
update-cm-9-20120415-SNAPSHOT-p4vzw-signed
I did not install the systemUI file, was I required to do that?