trouble recognizing external devices..... please help

if anyone could give me advice it would be greatly appreciated.

i have two items that are canon (film scanner and powershot g5) which
connect through usb ports. the canon film scanner used to work on my
system (working on windows xp) but no longer recognizes the item. this
is a work computer and other people log on to use is because of the
film scanner. the only things that have changed in the last two weeks
is macafee was put on our systems and i connected a usb pen to my
computer, which it didn't seem to like. i have talked with canon's
support staff and they are sure it is not there product. i have
checked both items on another computer here at work and they function
fine so i know it is not the camera or the scanner. it seems to be my
computer.

has anyone run into this problem before and does anyone have any
advice for me.