Imaginary Lagging

It's an odd problem, but here's the situation. I sign on, with Second Life and Windlight. either one runs just fine. I sign in, i rez up, everything's cool. However, despite how quickly everything else rezzes and how no one has any problems, I seem to be stuck flailing my arms in a falling animation. I try to move and it's like I'm wading through a cement sea. I try to fly and my av is like 'nuh-uh'. I've reset my computer, reset my modem, reset my router, checked my network status, tried other internet apps with no problem. What the hell? Why am I being shafted like this.