I had to do a system restore in XP, after the restore I tried to run WAU, but it crashed saying "Application cannot start. Contact the application vendor."
I have run the .NET installer and repaired the installation with success, or so it says :)
I have tried uninstalling WAU, but it won't even give an error, its just doesn't work.
I have tried reinstall WAU through IE7 and FF, getting the crash error.
I have tried downloading the ZIP folder and installing it locally, getting the same error.
Dunno if it will help, but attached the exception log as a text file.
Update: problem fixed
I am not entirely sure which of the below steps actually worked, but heres how I got it to work when getting the "Application cannot start. Contact the application vendor." error after a system restore.
Deleted C:\Documents and Settings\<user>\Local Settings\Application Data\apps\2.0
Deleted the following registry key (Typing regedit in the commandprompt)
Deleted the temp folder in C:\Documents and Settings\<user>\Local Settings\Application Data\Temp\WowAceUpdater
After this I was able to reinstall WAU and now it works like a charm.