aakk9999 - 8:05 pm on Oct 14, 2011 (gmt 0)
Tedster is right that it is not possible to get 30,000 duplicate titles from the description of what happened. If a character of URL was removed, which in turn caused (lets say) that "old URL" redirect to a new URL with removed character, then Google would never report duplicate title.
The only way of you having a duplicate titles would be the influx of URLs (with removed character?) returning the same content as the old URLs. In this case, even if you set up redirect from "old" URL to these "new" URL (with removed character), Google will not be able to see 301 redirect until Google re-crawls the old URLs. This would result in duplicate titles showing in WMT for a period of time, until all "old" URLs are re-crawled.
So I think you really need to ask your developer what did he exactly do and in what order, especially whether he set up 301 afterwards in order to try to rectify the missing character errors?
It would be wise to know exactly what happened so that you do not end up sending 301 back and forth between "old" and "new" URLs in order to rectify the problem.
<added> What URLs are currently linked from within the site - old URLs or new URLs with missing character? I.e. do you now have lots of internal 301 redirects (site shows old URLS that do 301) or does the internal links show new URLs with missing character?</added>