Hi,
The CCES tools do not access the COM port. Can you check the Pre/Post Build options on the failing machine via Project: Project Properties: C/C++ Build: Settings: Build Steps. Are you invoking any external tools using these steps?
Can you try running the CCES tools using "Run as Administrator" by finding the "cces.exe" in the CCES installation directory, right-clicking, and selecting "Run as Administrator". Does the same problem still occur?
What if you build another example - does the same error occur?
Regards,
Craig.