I've made a few short vids using the in-game rendering engine and never had a problem. Last week I changed the size to 800x600 and ever since the movie renders as a black screen with audio, then I have to ctrl-alt-del because LOMAC hangs. I did a fresh install of everything and still get the same result. I'm still waiting on Ubi tech support to get back to me so I thought I'd post it here as well. My spec:
LOMAC:FC 1.12b
CPU: AMD 3500
MB: Asus A8N-SLI
RAM: 2 gigs PC3200
Video: Nvidia 6600GT (SLI)
Audio: SB Audigy 2

Ubi is not going to reply.

I really don't understand what happened, and why a fresh install of LOMAC did not fix it.I even cleaned out the registry. The only thing I can think of is to get the latest nvidia drivers.

Like Konny said, UBI are not going to reply. They baled on Lockon after patch v1.02, so you would more likely get an answer if you post your problem on the Developers forum (Eagle Dynamics)....

http://forums.eagle.ru/index.php