Very very anoying problem with jQuery!

Very very anoying problem with jQuery!

Hi
 
I am doing a JSON callback that does a dom update via .val and .html methods, this is bound to a click event.
 
This works fine, and in IE8 and Chrome I have no problems.
 
However in FF (3.6.16 and other versions) the screen blanks completely to a white background for a second and then comes back.
 
This not only gives me a headache but will be awful for users.... I just don't know why FF does this and is it a common problem?
 
I'd rather do a normal entire page refresh than have this headache inducing side effect... really need some advice )
 
Thanks.