XP may very well be the problem - I cannot test it here.

If a simple test form does indeed open and close the port repeatedly without giving you this problem, there must be something else in your production form that is not letting the port handle to be released properly. After you have issued your port close, check the value of CommID of the control. What do you get?

>Jim
>I'm not using any handshake protocols. The scale is set to send text data in a continuos stream. ( In fact, the cables are connected one way only, send in data ).
>Given that the data streams non-stop, its not possible to clear the buffer.
>Could it be that WIN XP is keeping the session alive in the back ground somehow? Any way to check?
>Thanks
>Yau