Hi Jonathan,
So, the IDATA is used for call stack as far as I know. But an error may also be falsely triggered by a) reset via brownout, unhandled interrupt or otherwise b) communication loss between debugger and chip.
Could you perhaps click inside the Disassembly window and step by each instruction near where it fails to find out exactly which instruction causes the error?
Also, you can click on view ->Memory->IData. You may have to select something else and then idata again. bytes marked 0xCD have never been in use.
Also, view->Stack will give you an overview of how much is used. Keep an eye on these while debugging.
Also, if you look in the memory view and the register view and the disassembly view when it fails, a communication error will show up as 0xFF in most all values in these windows. This may indicate a reset, or other unexpected action.
Best regards,
Aslak