tedster - 9:21 pm on Jul 7, 2010 (gmt 0)
There are a number of recent posts here about WMT data being off - but none have been about a "too many URLs" problem. That has historically been a very real warning to the site owner.
I would say check out some of these URLs and see how your server responds. Google will crawl not only URLs from your sitemap or your site's internal links. They will naturally crawl URLs that they find in external backlinks, and if an incorrectly configured backlink ends up resolving 200 OK on your server, that can start a cascade of "bad URLs".