When you reinstalled poser, have you tried installing it to a new directory or a new folder that didn't contain your old runtimes?  Because even when you uninstall, all the runtimes libraries are still remained (which it should) and along with your old personal info and preference settings.  If poser runs fine on different location, than the culprit probably lies within those settings or even in the runtimes. 

For me, when I had this "buffer overrun" error, it was caused by me creating a simple windows shortcut under the character folder in one of the runtimes.  I did this so that I could move easily between different runtimes when I needed to work on the cr2's.  But when I started the poser, and when it got to the part where it was loading the library, it just crashed after giving me that error message.  I doubt you've also created these shortcuts but just letting you know that even the simple things like shortcuts can cause the crash.

You said you installed the recent poser update, so maybe that could also be the cause.  Does program runs fine with the SR2?  It really gave me fits trying to figure what was causing the "buffer overrun" because, essentially, it could mean anything.  Just try to think of all the changes, even the minor ones that are done recently, not just to the Poser but to the computer.  I hope you get yours sorted out.