Perhaps the fast ram modules on the CSPPC are not tolerant enough for 66Mhz? If you have different ram modules, give it a try by swaping the existing ones. It could be that the problem manifests itself only when the CVision is used. Other than that, you could also try to set the PreCharge option to "on" for the 68k cpu within MK3 early boot settings menu and see if that makes any difference.
