[RoundersRocks!]

You do not include your table image in your description of the hand. I am guessing you have been betting alot and this player might be ready to call you down with something. In my experiance if someone thinks too long about a flop call, it usually indicates that they are committed to call the turn. Either take the free card or make a bigger turn bluff. I lean toward abandoning the hang.
You might win with a bluff, you might not, but if your at a table of weak/tight/simple players, why not sit back and wait for a place where you are more certain. A big part of playing LAG is knowing when to backoff a bluff.