That error is bad news. It means that the file it is trying to patch is not exactly what it expects to find. This is almost always caused by one of two things. Either you have a virus or a hard drive error. I'd recommend running a virus scan and disk scan. After that, you can only get the update by either downloading the full version or if you still have the downloads of previous versions that can still get you up to 1.08 patch 6, you can install those again before installing the 1.09 patch.