[mchannon]

Don't do anything rash.

Cofounder could be having a mental breakdown and/or just have decided to get really drunk or stoned.

It could be something medical and/or embarrassing.

Some people have inner flakes that exert themselves at random times. I'd give it another week; during that week figure out:

a) How you can ensure this doesn't happen again if the guy comes back into the picture and b) What taking the hint actually entails. It should probably involve folding up shop, mailing papers, and starting something new without the cofounder.