Yes; inspect requests were actually throttled in 3.3.5. I'm not sure if they throttled it further in 4.0.1 or not, but addons should expect that many of their inspect requests will never actually happen. It sounds like TipTacTalents may be getting stuck waiting on an inspect; check for updates, and then report the problem to its author. I think he mainly uses WoWI.
inspect and all related events are currently not working properly.
sometimes you can inpsect another player, sometimes not.
this has nothing to do with addons or the 3.3.5 restriction - this can happen if you play without addons.
hopefully blizz fix this strange behaviour soon...
My tooltip addon will add the "Talents:" line followed by "..." while it waits for data to be gathered. With this bug, that line doesn't even show up. Though it was behaving on live last night as opposed to on Beta.