"multiple files 'included' in the main file."

Could this be your problem?

This certainly causes problems with 'C' compilers:
The debug info in the Object file supports only line numbers; it assumes that the line number info in file.obj refers to file.c.

Now if you #include files, you are effectively combiniing several different files before the compiler even starts - so the debugger can no longer relate the line number info in the object file to the actual cource files!

Have you tried assembling your files separately, and then using a Linker?


"JTAG connector (10 pin IDE connector)."
I presume you mean "IDC" connector - you don't need a disk drive just for JTAG! ;-)