Has anybody come across this one before?:

1) I rendered my project out as a Lagarith master
2) Loaded Lagarith file into a fresh project, with screen settings matching the file.
3) Created a wmv preset for:

Windows Video 9 (not advanced profile)
2 pass CBR
High Definition (1440 cx 1080)
25M
Frames Per Second 25
Seconds per keyframe 2
Override Default compression buffer (seconds) 8
Video sharpness 90

4) Rendered test portion to check it is rendering ok. Seems to work.
5) Rendered whole project.
6) Rendered file has only audio element present, no video stream has been rendered (despite it taking it over 16 hours to not do it).

Why, why, why, why, why, why, why, why, why, why, why, why, why..........?

EDIT:

I should say, this is one of my first render attempts in 8.0c. I had random missing image issues on a previous attempt to use this software when rendering Mpeg 2, but this was the screen blanking rather than no video stream being written at all. I have to stick with 8.0c because I need to make use of the 5.1 mapped wav file support.