IMHO, I've found over time that all versions (From Acrobat 4 and early version's of Pitstop caused some strange incidents. To be fair most of the times it was older versions of the combo but sicking with newer versions of both products is much more stable. But let's not be all that nice as you can tell by the amount of updates both products produce every version that something is indeed going on. Although Acrobat has a lot of "Security" fixes it just seems to me and my co-workers that Acrobat has always been the weirdest product of the Adobe suite. Interface is a mess, shortcut's don't to seem closely related to other Adobe products, etc. etc. Don't even get me started with Enfocus. With all that said I can't live without either product, well I guess I wouldn't have a job if all products worked as advertised. For most of my year's I always thought most Mac's didn't have the horsepower (RAM) to run comfortably enough. Not the products fault. Font's cause most of the crashes and corrupt cache accounting for a little bit of the mess. Once you master Pitstop your prepress life feel's complete. I am by no mean's close to figuring it out but when it works it truly is a great product. I was using Pitstop 10 at my last job with the usual licensing issues popping up requiring a reinstall and at my new job (First time using it on a PC besides Server versions) also required a reinstall using version 9 of Acrobat and Pitstop. Acrobat didn't like the updates and Pitstop once again had a license issue. I believe both applications are processor intensive and if your computer hasn't go the oomph, update it. You never mentioned how much RAM you were using nor how powerful your machine is.
Like I said I love Pitstop when all is well but beware of the gremlins.