Sometimes the lock-up results in a "You have been disconnected" dialog after about 30 seconds. I can click OK on the dialog and reenter the game from the character selection screen. But occasionally it will cause the client to close completely. I have lost quest progression progress twice now. I am getting really good at killing the skeleton king.
I updated my graphics card drivers, Windows is up to date, I run in admin mode. The problem still persists.
Graphics Card: NVIDIA GeForce GTX 470
OS: 64 Bit Windows 7
Ram: 4 GB
CPU: Dual Core 1.8 GHz