Just a few ideas
- think of the partial refresh as just another ajax/javascript event being triggered,
- try and find an error by using IE debug tools.
- create a new xpages and move in pieces to it one by one to find the object causing the error.
- will it help to trigger the partial refresh using your own code
http://www.xpageswiki.com/web/youatnotes/wiki-xpages.nsf/dx/Work_with_events_and_partial_or_full_refresh
Thomas