SteamCMD help

So basically, whenever I try to app_update 4020, it goes on downloading like normal, but ends with this error code:

Error! App ‘4020’ state is 0x602 after update job.

This also happens when I try app_update 4020 validate

If it has anything to do with it - my stupid antivirus software deleted a huge section of code in my server including everything attached to it. Which also broke my gmod. Please help, I spent a lot of time getting my server the way I wanted it.

What OS are you using for the server?

Windows 7

[editline]29th June 2013[/editline]

UPDATE:
I originally had the install directed into a folder directly in my C:
I changed the directory to a folder in my documents folder and it worked! ^-^