I used it successfully just the other day--frameserved a "nested project" on the Vegas timeline straight into a proxy avi, then opened the avi in Sonicfire Pro to score music. Why it works, I don't know. But I have 6b installed. Perhaps double-check that your Frameserver plugin is the most recent version?
I found out the problem on the debug mode help faq. It won't framserve out with your project properties set to 24 bit audio - it can only happen if your project is at 16 or 8bit audio, no matter if your audio tracks are muted.
That's probably why I keep getting error message, I never thought the audio would cause the problem. I'll try to do this again, thanks for mentioning this.
Confirmed, that it's the 24-bit audio that's causing the problem. I can frameserve right away when I changed it to 16-bit. Really thanks for the info!!