I only did it a while back to have one amp facing me, and one facing out, more as a monitor. A friend of mine who is an electrician bought me the larger amp and the hook ups between the two, and I've never had a problem. I don't do that anymore though, since one amp stays at university and one stays at home. I would have never thought of hooking them up together anyway, but since the guy that bought it for me said it'd work fine, I did.
And Gizmologist, I have no idea what that really means, but perhaps that's what is wrong. There could be debris in the key that's for certain. I'll have to get someone to look at it I suppose.