I love the changes, though with the info tabs on the right, it seems a tad odd to have the little poster info boxes (You know, your avatar, username, basic info) next to each post appear on the right as well. Everything else looks great! :3
I need to get back on to this site!
I have proper grammar, good spelling skills, organizational abilities, and the ability to condense things.
The last point is proven by the fact that I compressed my useful writing skills into one sentence. >:3
May I help?
My guess is that the stress if cohabitation finally caught up with him. If you want to be certain, take him to a qualified vet in your area and have an autopsy.