Trees being messed with

This happens sometimes when a tree merge is in progress. If might clear after awhile, or you can look for parent conflicts going back from your profile.

It could also be that someone found bad information and the tree was cut.

One more possibility is that non-pro are limited to seeing 5,000 in their stats and that stat for you may have been set due to a bug.

Regardless what, if I see this, you still have over 100.000 ancestors even if that's not showing up in your stats.
I myself can only see 5000, it is due to a limitation, but I'm also not a pro.

http://www.geni.com/path/Ulf-Martinsson+is+related+to+Susan-Muir?fr...

Here's the official definition:

http://help.geni.com/entries/472931-Blood-Relatives-vs-Family-Tree

For non pro's I see a limit of 5,000, for pro's a limit of 100,000. I think Jonathan is correct in his analysis; I had gone down to 5,000 once and it was a backed up computer job, fixed itself with a little patience. Do "walk the tree" looking for conflicts though.