NTVDM CPU has encountered illegal instruction

I'm a real noob, so be easy on me at first.

I have started easy and was able to program 'Blink' to get my feet wet. It worked!

I tried some code written for the basic2 stamp after some mods to make it PBP compatable, tried to compile and program and encountered an error msg that I can't shake! I have even tried to redo the Blink programming and arrive at the same error msg.

'16 bit MS-DOS subsystem
Micro code Studio
The NTVDM CPU has encountered an illegal instruction
CS:0ddc IP:2224 OP:ff e9 6c fe eb

Choose to close to terminate the application

Close Ignore'

Anyone have this problem before?

ps I have been able to go to command line and 'PBP -16f688 blink' and call pbp up using the icon and program the chip,

XP op sys

I just started getting this same error message out of the blue today.
Tried restoring the NTVDM files in windows XP, scanned for viruses (the WWW info suggested that).
Later discovered I could still compile other code for other PIC types (was using 12F675 initially). I then installed a second new and fresh copy of PBP and pointed MCS to compile from the new copy. No more error messages....

Looks like PBP or the Assembler was corrupted.

Cheers,
Martin