[Ian Schorr <ian.schorr@xxxxxxxxx>]

The biggest problem we've had recently, and the source of most crashes with largish captures has been the 2GB per-process limit of 32-bit Wireshark builds on Windows (a limit of any Win32 app).  Memory usage on captures with a million frames can easily hit this limit, and the process will immediately fail un-gracefully as memory allocation is impossible...Especially depending on what memory-hungry features you have enabled, and what memory leaks you're hitting.  

I assume you're experiencing (or will experience) the same - if so, pursue 64-bit, and potentially a non-Windows OS.