I upgraded from WPMU 1.2.something to 2.6.5. I did it in sequential jumps 1.2.3->1.2.5->etc. up to 2.6.5.
Categories didn't transport across, neither did tags. When I try to add new tags or categories, I'm told that 'Could not insert term int othe database'. Could it be that hte database didn't upgrade properly? Have I got a permissions error somewhere, or has the database changed to accomodate tags & categories in new fields/tables?
Could do with some help here, if you have time... ;-)