Let me jump in as I might be having a similar problem.
For me, I have also had a few weird issues, after upgrading to 1.2 OS, never had problems prior. I upgraded so I could install my new CF reader.
Exact steps with most recent freeze:
1. loaded my PGM, then loaded my sequence.
2. Played sequence, then went to add an additional 8 bars, as soon as I turned the wheel to add bars, the screen went to this:

I could hop around through these weird screens, but had to reboot, as I could not get back to the normal interface.
ever seen this?
I had two other freezes last night, add while adding to my sequence, but the other two times it just locked up...
It is just a guess that this has something to do with the 1.2 upgrade, I know how software upgrades can cause as many problems as they fix sometimes though I really hope this is not the case here.
Unfortunately, I doubt there is any way to rollback to 1.1x if I needed to, is there?
any ideas? anyone think this could be bad RAM acting up?