sorry Thomas but i don't agree.
The way a genlock is recognized on an Amiga, is totally different. (via the XCLK and XCLKEN)
I have since a life, a 1084 connected to the Amiga RGB port (switched OFF quite always).
@Patrick
the fact that you have no problem with an A520 and/od a VGA adapter, let me think that you have a problem on the Amiga 23pins>1084 cable (a ground loop or something that charge too much the H/V Sync lines)
EDIT- ahhh . . . . understood now.
You had a 23pins>VGA direct cable installed? (without the VGA adapter)
Ok now . . .as never said :-)