Should I call the all in??

[Bartman387]

This came up on Full Tilt $5+.50

Hero BB with JJ, has roughly 2000 and is level 4.
UTG calls, UTG +1, who is a very tight player goes all in for 750. folds to the hero. After much thought I fold.

Should I have called?? In hindsight I think I should have called as I am way ahead against a random hand, but considering the player I put him on AA, KK or A-J,Q,K. I seem to tighten up considerably when forced to call an all in, even when I have the villain covered and have paint. What thoughts goes through your head as you determine whether to call an all in?

Results below in white:
<font color="white"> UTG calls, shows K6s, UTG+1 shows AJs, One of the lower hands I put him on. flop is a blank rainbow. Turn J, river blank. UTG+1 wins with a pair of Jacks. </font>