Repeated client crashes on Frostwolf when starting game

About 1/3 of the time when I try to play on Frostwolf, my client crashes when I'm logging onto a toon. I got this error message tonight:

This application has encountered a critical error.
Error #132 (0x85100084) Fatal Exception!
Program: Wow.exe
Process ID: 10168
Exception: 0xC000005 (Access_Violation) at 0023:00ECA3BD
The instruction at "0x00ECA3BD" referenced memory at "0x53494C6B".
The memory could not be "read."
Press OK to terminate the application.

Any ideas what is causing this and how to fix it?