No problems for me either, on XP.
The only quirk I've run into is -- whoops, two of them, both relating to avast:
There's two or three avast files (at least one of them a DLL, if I remember) that keep turning up in the "Pending Files" list.
And the Web Shield keeps showing up in the firewall log as blocked. But it must be working properly, since the "scanned" count looks about right at any time.
In both cases I typically find those after I've gone off-line, so I can't "submit" them for approval. In the second case, too bad there wasn't a right-click context menu for the log so I could grant remembered permission right from there.
And in both cases they seem to be along the same lines as the "cosmetic" mouse-over problems in Comodo 2.4, look serious but don't actually affect anything improperly.
I think they changed too drastically from 2.4 when upgrading, and it (particularly the interface) seems a lot less user-friendly now, but hopefully everything's still working the way I want it to. I've got both parts set for learn-in-safe mode, which is probably the best way to go.