So for starters, I'd try without Mumble running, or at the very least ensure that the mumble overlay is disabled if it is not already. This is on the Tweak for Framerate page of ISBoxer. http://www.isboxer.com/wiki/HOWTO:Tweak_your_framerate

You also might ensure that InnerSpace and WOW are running the same "bitness" as per this post. http://www.isboxer.com/forum/viewtopic.php?f=22&t=7091
While you are launching, so the initial reason for that post is resolved, this will help eliminate any other potential crossover on this issue.

If you are using wireless, then use wired (I'm not sure this was ever answered), I think it was just left as a don't do it, and assumed that you weren't doing it.