Error in JQuery.js?

Hi All, Wondering if any of you have found an error in JQuery.js? I was writing a script using JQuery today and firebug complains about an error in line 1772. The statement in this line is: return fn(elem, i, m, r); The error message I get is: fn is not a function. Wondering if this is a known issue? Or if there is something else thats wrong with the script I have written? Thanks