Which version of MSN Messenger for the mac are you running?
There are updates on the MS website, but with regarss to video, the following message was announced by MS
"Microsoft has responded, and the rumors of Messenger's demise were exaggerated-- Messenger 6.0 will be included with Office 2008, and Messenger 7.0 will have audio/video capabilities included, and will be beta testing soon."
So no development, till the new versions are released now.
Otherwise there are a number of MSN Messenger compatible clients, that may provide the features you are looking for.
Try the following for starters
http://www.mercury.im/
http://www.adiumx.com/
Hopefully one of these, will have what your looking for, if I find one I will let you know.
Hope these help
Dave