When i click on a story...a page comes up that says "sorry, bad request"?

it also reads "size of request header field exceeds server limet"....I also can not add any comments or vote on others comments.....this just started to happen.....I am not doing anything differant then what i was doing in the past but now it does'nt work....can someone help.....i dont know anything about computers...one day it worked fine...the next it did'nt.....it worked just fine for the past 2yrs...now it does'nt