Wikimedia Bugzilla is closed!

Have a look at
http://www.mediawiki.org/w/index.php?title=Extension:FireStats&curid=9420&action=history.

If you click 'last' to compare the diff of 00:15, 28 November 2006 "(sort key)"
to it's previous version, and then use the 'next diff' buttons to step through
the diff, you will need to click it 10 times to reach the item just above it in
the list (as opposed to 1, as you would expect).  This item was an import.

I'm guessing that the problem is that on the history page the edits are sorted
by date, but when using the next/last diff buttons the list is ordered by ID, so
the imported pages, which have a newer ID but an older date, are ordered
incorrectly.