[quote user="Chester Gillon"]Therefore, the problem appears to be caused by a change in how the MSP430 v4.2.x compiler generates the symbolic debug information.[/quote]The project was created using the default output format of "eabi (ELF)".
If the output format is changed to "legacy COFF" then when the MSP430 v4.2.3 compiler is used the debugger resolved the correct address of ADC0 to ADC3 in RAM, and displayed the correct contents of those classses. i.e. the problem appears to be the symbolic debug information generated for the ELF eabi.