I'm observing the same tendency of these apps to crash after a prolonged period of use. I have 2GB of memory (Mac Pro 2.0 ghz).
The pattern is that one of the three will unexpectedly quit, followed by instability in the others (e.g. unexpectedly quit error trying to open Adobe Help; or the other apps themselves become unstable, quitting on the attempt to do basic things like create a new document, save to disk, etc.).
As you state, the only way to recover is restarting.
I think these are memory related problems in Rosetta. I actually got an out of memory error once, trying to place a TIF into an InDesign file. Activity Monitor showed almost no free memory at that point (the green part of the pie), and a large inactive portion (the blue part). Although quitting apps restored free memory, I couldn't get the Adobe apps to run at all short of a restart.
I'm using Apple installed ram; 3 internal SATA drives that were formatted by me (zeroing data); and the latest releases of Adobe software. Hard disk, processor and memory diagnostics (Techtool Deluxe via Applecare) all come up clean.