http://www.wizards.com/default.asp?x=dnd/rg/20060321a

From the article:

It's possible to attempt a trip attack as an attack of opportunity. Fortunately, you can't be tripped while getting up from prone, at least not through the attack of opportunity you provoke. That because attacks of opportunity are resolved before the actions that provoke them (there are a few exceptions, see Rules of the Game: All About Attacks of Opportunity for details). When you try to stand up from a prone position, the attack of opportunity comes before you get back on your feet. Since you're still prone when the attack comes, the attack of opportunity can't trip you.

Ahhhhhh nifty. Ok then, I guess wolves can't trip lock someone. They could, however, ready their attack for you sucessfully standing up....

However....you can still disarm....just to be a bitch....and then trip when they take a move action to go for their weapon....and then disarm......>_>

hahahahahaha