Hi .. you have to also make sure that your comm port isnot being used by another device when running your app (such as. HyperTerminal, Modem, etc)

you mean by this to not have the hyperterminal connected or a modem connected to the port?

The weird thing is that the port is communicating fine.

after some ours of work i get the error message.

What i am doing is opening the port when a textbox lost focus, to show the weight in another textbox.
when the user press the save button i close the port.

this is a repetitive task.