ASYNC.PAS closing app error?

Hi there

I am using ASYNC.PAS for my serial communication (with an Intel 8051
development board). But I have noticed a very bad problem.

I use use CloseCOM(COMport); where COMport is a variable that holds 1,
and was used to open the COM port for this session, as the last
communication command from ASYNC. Yet after starting my program again
I cannot get contact with the development board, unless I do one of
the following:

When programming under W95:
- Exit the DOS Window, back to W95 OSR2, and open it again and start
the application.
When programming in plain DOS 6.2 /7.0
- Reboot the machine and start plain DOS over again, then start app.

Are there anything I should do besides call CloseCOM(COMport); or