Congratulations, sandlwood.
I've just tried Add/Remove Programs> Avast> change/repair (as you did) and came up with the same result: 'Error processing packages. Please use full update.'
OK, so update now brings up Engine and Database update Step 1/2 File download vps_32-b71-b70.vpx where the Overall Progress bar gets to about 5mm along, then hangs for 4mins 17secs. Clicking OK confirms connection enabled and update confirmed with time and date. Home page also confirms 'Everything up to date'.
Clearly, this is wrong, for I'm still on 130802-2.
Considering this thread has been viewed in excess of 520 times, it would appear to be a major problem for Avast free users. Would it not be appropriate for Avast officially, to make available some kind of fix that doesn't involve a complete uninstall/ reinstall?