Download issue with Cataclysm

Hello,

I have a pretty high level character but it's in the Cataclysm expansion which I've been trying to re-download but I keep running into the same problem. When I click wow.exe, it begins download the 'required files' but it always ends with this error:

The system cannot find the file specified.

Program:
C:\Users\SHPONG~1\App\Local\Temp\7zO8C1.tmp\Wow.ex e
ProcessID: 5760
File: .\Client.cpp
Line: 3623

file: signaturefile


Any idea what the hell is going on and how to fix this? I'd really, really love to get back to my character and continue playing with my friends. I downloaded Mists of Panderia just fine, although there was some bugs in the game, it still downloaded just fine.

Thank you.