[quote user="Chester Gillon"]One other suggestion to try and determine the area of the problem, can you try replacing the MSP430.dll in the CCS 5.5 installation with the one from CCSv4.2.5?[/quote]On further investigation, the MSP430.dll from CCS 4.2 isn't compatible with CCS 5.5.
The reason is that CCS 5.5 makes a MSP430_Configure (SET_INTERFACE_SPEED, FAST) call which the MSP430.dll from CCS 4.2 doesn't understand (and causes a "Invalid parameter(s)" error).