Did you download the patch yourself, or have the game check for updates?
Are you sure you got the correct language version? The English DVD version patch is 406MB (
Divinity II-Patch 1.03 now available).
Did you install the game from an account with administrator privileges? Maybe if the patch could not find the expected registry entries, that could be the cause of the error. Reverting to an earlier restore point or using an aggressive registry cleaner could cause problems, as well.
Try running the patch as administrator.
If you used a no-DVD crack, restore the original exe or the patch will not install.