I had similar problems with the updated Kindle 4 PC. I noticed that, on at least one occasion, my K4PC gave me a "C++" error before it crashed and burned. I checked, and I had Microsoft's 2005 and 2008 C++ packages, but not the 2010 (latest). I downloaded and installed the appropriate one (for me, Win7 64bit), and the latest version of Kindle 4 PC worked. I've had no trouble since.
You can either use my links if you're the trusting sort, or go straight to Microsoft and do a search on "Microsoft Visual C++ 2010 Redistributable Package "
http://www.microsoft.com/download/en....aspx?id=14632 (64-bit)
http://www.microsoft.com/download/en...s.aspx?id=5555 (32-bit)