Thanks Robin – I lose some customizations when switching themes so I’m just going to turn off the author option for now. I’m looking into canonical issues either from WP permalinks or Yoast, or something in bbPress 🙂 If I find a solution, I’ll report back!
I think I’ve narrowed down the problem to bbp Style Pack. It gives the option to show the author under freshness display, but making that visible under the profile/forum/subscription tabs is causing a conflicting url to be created. I think. I’ll post this with the plugin author and report back.