I recieved a letter from Canopus Tech support yesterday in response to my problems getting the ADVC-100 to output to my BETA recorder, and the ADVC-100 is in fact not compatible with BETAcam. Specifically:
"The ADVC-100 uses an internal sync which does not generate a strong enough subcarrier to lock onto a beta cam device properly. So this will result in odd color problem or even black and white video. The ADVC-100 was not designed to be used with Professional level devices."
The ADVC-500 is compatible with Betacam, but costs around six times the price of the advc-100.
Hope this saves somebody else some trouble.