Dog Is Suddenly Aggressive With Owner?

I've had this dog for a few years now--almost five. He's always been protective over me, and he's always been uncomfortable with men (except my husband). We recently got another dog, and he and the dog get along rather well. However, about three days after we got the dog, our old dog started becoming more aggressive specifically with me. Sometimes he would only growl at me if I peeked into his hide-y hole while he was in it.

The worst bit of aggression that he's had, has been literally in the last bit, where I tried to put his leash on him. (note: I never jerk his leash or drag him. He lashed out at me, barking, growling, and biting; he bit my hand pretty hard, and then kept trying to jump up to where I held my hand to bite it again. For the next few minutes, he stayed where he sat, growling at me, and refusing to let me near (I just wanted on the bed at that point, I would have gone around him, but he wouldn't even let me do that).

It doesn't seem to be a dominance issue, it's not a food issue either I don't think, but it definitely seems to be stemming from our new dog.
Any advice on how to counter his aggressive behavior and please don't suggest putting him down or getting rid of him.