Me too absolutely identical as everyone else "Last Encountered error: Invalid File Signature, Setup will terminate
Never once had a problem before and it's been running fine for ages
Tried Uninstall - and selected Fix Repair and up pops "Error Processing Package. Please Use Full Upgrade"
I'm running Windows 7, avast prog 7.0.1466 last successful definitions were 121003-01
Has anyone heard from Avast yet?