Works in the Simulator and ICE but not on the target Dallas DS87C520 uP

I have a program compiled to target a DS87C520. The source is A51 assembly and C code mix. The compiled output is in Intel Hex file format.

The Keil Simulator executes the program just fine. We also have an ICE that runs the program. However, when I burn the hex record into the actual micro, I get nothing.

Any ideas?

I can email source, hex file, etc if anyone wants to take a look.

Thanks,
Chris Beattie