I have a keyspan serial USA-19HS. I've installed the driver in XP. Using the keyspan assistent and testing the device is OK. If i use a app to use the device it seems to work and then fails. If i test the device in the assistant it fails. Disconnect and connect the device, using the assistant and the test is OK. But if i use the device it blocks and a new test fails. I will test the SerialClient now!