I've upgraded from v1.2 to v2.1. I had no problems with v1.2. However, since upgrading to v2.1 my sitemap is no longer generated.
I also noticed v2.1 is attempting to generate far more pages despite the fact that I unchecked both the text format for Yahoo! and the html sitemap.
The generator appears to perform for approx. 45,000 pages and then freezes.