Hello Chris,
The grounds in a home electrical system are there for safety in the event of an electrical fault. In the event of a fault, they are intended to carry the fault current safely back to the electrical panel.
Insteon devices do not place current or any signals on the ground conductor. Many Insteon devices are two wire and do not connect to the ground at all. Switches bond the ground to the metal switch frame in the event of a catastrophic failure (no connection in normal use).
You appear to be envisioning the home wiring as a balanced transmission line where the ground wire serves as a shield. I really wish that were the case. If it were, X10 technology would be equivalent to hardwired. Shielded twisted pair Wiki:
http://en.wikipedia.org/wiki/Twisted_pair
In contrast to the link above, our power lines are not twisted, unbalanced (wildly varying loads), and unshielded (the ground wire is a very ineffective shield). The powerline is an ugly communication path at best. Current automation technologies that use it get around the ugly path through high transmit levels (UPB) or distributed repeaters (Insteon).
Moving a ground wire within a breaker panel, from one grounding point to the next, should have absolutely zero effect on communications. It simply isn't part of the communication loop.
Tightening a connection on a neutral wire (which is what I suspect you accomplished) can absolutely affect communications.