Tricky this as its heads up (not something I dabble in very often) but I am gonna have a go.
While he could have a big pair or AK something along those lines hes prolly reraising preflop? A lot depends on how you have both been playing up till now but we dont know that so I'll go with what we have. If he has J10 (diamonds or not) then surely the flop is a good time to check raise if not lead at it although check calling isnt bad either.
If he figures you for an overpair then there arent many better scare cards than that turn to throw in the cheeky mini-raise. I think hes holding 56 and has you totally crippled, 78 or possibly 89. Of course he could have almost anything from a busted flush draw to a set thats now a fh. I think the key is the turn when he mini-raises I think he has at least 2 pair here and possibly the set and knows when you just call that hes ahead. I am folding.
Regarding the 1st hand you posted up and what Muze said about studying the hand in detail, if I had played that hand I am 100% sure I would have called (if not gone all in) looked back at it later and then figured out he had me beat. In the 30sec timer or whatever it is I wouldnt have been able to stick him on JJ, I am just not that good yet :P I am happy though that after studying it for a while I got somewhere near the right answer
Edit: damnit, looks like I just copied everyone else

but I didnt read any of the replies before I did mine
