Radí kompletně přeinstalovat, nebo dle postupu:

An attempt was made to move the file pointer before the beginning of the file.
Go to your World of Warcraft program folder and look for the following files. If you find them, delete them.

Inside World of Warcraft\Data
common-2.MPQ
common.MPQ
expansion.MPQ
lichking.MPQ
patch.MPQ
patch-2.MPQ
patch-3.MPQ
Also delete the Cache folder inside the Data folder.

In World of Warcraft\Data\enUS
patch-enUS.MPQ
expansion-locale-enUS.MPQ
expansion-speech-enUS.MPQ
lichking-locale-enUS.MPQ
lichking-speech-enUS.MPQ