g1smd - 5:47 pm on Mar 15, 2010 (gmt 0)
Make sure that your old canonicalisation rules are modified to point incorrect old URL requests directly to the correct new URL, instead of having those rules send old incorrect requests to the old versions of the correct URLs and then redirect again onwards to the new correct URL.
As an example, you might have had a canonicalisation rule that redirected
www.example.com/?id=123. If your new URL is
www.example.com/page123 make sure that both
www.example.com/?id=123 requests now redirect directly to the new URL, not from A to B to C in a chain.