Autoblog feeds not working

Hi

I use your Autoblog plugin on multiple sites. For some feeds (including these from other Wordpress sites I have set up) it won't process the feed - for some feeds this problem appears permanent, for others it appears to come and go. I get the following error message in the dashboard:

This XML document is invalid, likely due to invalid characters. XML error: Mismatched tag at line 220, column 19

(Diffrent line and column numbers, obviously, for each problem feed).

Can you assist?