[jQuery] Ajax - synchronous ajax call timeout

[steve_f]

Has anybody implemented a synchronous ajax call with a timeout. I
cannot get the timeout to fire, instead the ui just locks up, I cannot
really have this in a live environment, it would really hack a user
off!!!
I am trying to use the synchronous call to compliment a client side
asp.net validator therefore I need to wait for the return value of the
webmethod. Anyone got a good approach or solution.
Thanks