The file "C:Program Files (x86)\DiabloIII\Updates\d3-0-9558-Win-final.MPQ" appears to be corrupt. You may need to download this file again.
Please don't make me download everything again.
How do I fix this. I bet I am not he only one.
To make it clear I am already past the Updating files, I have the launcher up on step one in which it is supposed to complete the install, that means I am a hair width away from the game being ready for tomorrow. It is at this moment that I get the error. Everything worked up until this last possible step.
This was the anwer. Thank you Jerold.
I got that error too, but I fixed it pretty easy.
I went into the Program Files (x86)\DiabloIII\Updates folder, deleted the d3-0-9558-Win-final.MPQ file first of all. It's a patch file and not very big (since it screwed up in the middle of downloading), so don't freak about destroying it.
Then I made sure my firewall and virus scan was temporarily disabled before restarting the download, and I ran D3 as an Admin. After that, it downloaded smoothly and sucessfully.
EVERYONE THANK JEROLD WHEN THIS FIXES YOUR PROBLEM.