Cliff,
Two questions:

1) Are you using the S Video straight out of the Escient or coming out of the VGA output and downconverting the signal to S Video?

2) Is your system (TiVo, et al) connected to a CATV feed in any way? Since you mentioned the potential involvment to TiVo, They (CATV) almost always seem to be the culprit in grounding problems.

Good Luck

Rob