Vista - DVR software - remote IE view works in XP&Vista Home but not Ultimate 32 or 64

Hi there
I couldn't find a specfic forum for this question, so sorry but it had to go here!

I am running an 8-channel DVR card for a shop's security and it works fine for the most part. However I'm having troubles with the remote view through IE (via ActiveX controls) It works fine from any XP machine and it seems from Vista Home, but not from a Vista Ultimate machine (and I've tried from both 32 and 64bit versions) - The conection is fine, IE brings up the same interface, but the video images do not appear.

The manufacturer can't (or won't) help me out with this (as from his point of view it works fine as he has a Vista Home machine that can login pefectly) so I was thinking there must be someone who might have an idea of something I need to tweak.

I've tried turning off all the fancy Aero stuff, different graphics modes and resolutions, to no avail. I've tried disabling firewalls also.

Does anyone have any idea where I might start tweaking next? I could understand if I couldn't get it working from a Vista machine full stop, but considering it works from any XP machine, and from a Vista Home machine, there must be something I'm missing!

Any help would be appreciated.