MacUpdate app crashes on launch

I am running it on my Mac Pro, latest Mavericks version, and latest version of the app.

It is unusable right now since it crashes on launch. I get this in the log:

Application Specific Information:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFNumber length]: unrecognized selector sent to instance 0xf9762fc7990df37'
terminating with uncaught exception of type NSException
abort() called

Any idea how I can fix this?

I tried deleting the plist files etc. No luck.