There are bug reports for FC6 regarding the breakage of dragging messages being out of order for Thunderbird. There was not any when checked for seamonkey for development at the time. I added a report for development and referenced Fedora Core 6 being broken also. Will the patch with a variation work for seamonkey too?
Jim
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=225020