Yahoo web cam Grrrr!! Can't get it to work in Yahoo IM ?

i have used Yahoo IM for over 10 years. I have had the same web cam and it works in msn chat and other places BUT in Yahoo it says no cam found... I ever went to far as to get a NEW cam. Neither works. The cam shows as three in my control panel (XP) However in Yahoo IM preverences it wont let me choose it as a source. Like it is not there ..... HELPPPPP!!!!