As strange as this seems, when I changed "Maximum number of users that can be invited to a Private Topic" back from 50 to 25 (the default), the problem was gone. (The problem happened after I changed it from 25 to 50, strangely enough.) Anyone know why this would happen?
That's extremely strange. Franky, I can't think of any reason why that setting would have any thing to do with the original problem, but if it fixed it..great I'll need to fiddle on my test board and see if I can duplicate.