Cannot use USB video cam

Hi - I've got an analog camcorder connected to my laptop (running XP) via
an AverTV USB connection. I can output from the camcorder using the
supplied AverMedia software as well as Windows MovieMaker and other video
capture programs without any problems.

However, Messenger (V4.7.2009) dosen't like this setup. It does report the
AverTV setup as available when in the Audio Tuning Wizard, but when I
proceed from that screen, I get an error message saying
Camera error - The camera you selected is not working properly or may be in
use by another program.

Other than Outlook Express/IE I have (I believe) no other applications
running according to Windows Task Manager, so am at a loss to know what to
try next.

Any thoughts would be greatly appreciated. I could of course throw in the
towel and spend another £30 on a dedicated webcam, but I would like to get
my existing equipment working if at all possible.

I have not been able to set up a live video connection yet, so presume that
it is not a firewall issue (yet).

Russell Ridout