Scott:
If you want to be totally safe as to restarting the code in you program you should try to get a hardware reset to happen. Even the Keil start up code makes assumptions that the SFRs and other registers are in their wake up hardware reset states.

Two ways.....to get the reset...
1) If you have a watch dog timer let it timeout and cause the reset.

2) Otherwise arrange some external logic off a port pin such that a low level on the port pin invokes a reset at the reset pin. The reset logic will race to put the port pin back to a high level thus turning off the reset pulse drive. But that is OK becasue by that time the reset is already in process.

Michael Karas