Ok, more like aroud 80%, but it means that frames are dropping like crazy, and so it's completely unusable.  This is the first time I've used Capture since installing 5.0b.   It uses 80% CPU even when it is not doing anything.
I went back to Vegas 4, and things worked fine.
Any ideas what could be wrong?  I'm using a non-admin account on XPSP1.