Being in bands is a very stressful occupation. There are so many weird characters out there in Musoworld. Being a bit weird is probably a big reason why people get into playing music in the first place.
Monkey, I can completely empathise with your situation, and agree with the assessment of the other guys here, that your guy is just fobbing you off with excuses because he doesn't want to come outright and say it.
I'd have a serious talk with him, state your concerns, and give him one last chance. If he can't make rehearsals enough of a priority in his life, then he's not going to do you or your band any good.
I am truly blessed at the moment, having recently joined a band where everyone is keen, rehearses, is pleasant, and is technically proficient. Having just left a band where getting rehearsals organised was harder than getting blood from a stone (and no-one had learned the new songs either, when we actually did rehearse), it now feels like I've gone to heaven.
Hope you can get things sorted with this chap, or can get a quality replacement.