We've found that customers who have this problem have solved it 1 of 3 ways. The first way is to verify that the file is not being blocked via your anti-virus software (like Norton)
The second was to uninstall, reboot, re-download and reinstall the game. We've been told that this may not work the first time and 2-3 attempts may be needed.
The third method is to locate a PC that does not have this error and to copy the entire BIN folder (located in the \KingsIsle Entertainment\Wizard101\ folder) to a portable hard drive or Memory card and then COPY over your existing BIN folder with the working copy.