You say you used a 6V regulator on a 6V batttery? If that's the case and you didn't use Li-ions or Li-polys, then the voltage to the RX probably went below the required threshold and you lost response out from the RX to all of the servos.

Tom, does this make sense to you (i.e. putting a 6V regulator on a 5-cell 6V NiCd or NiMH?

Bobby