The IO operation has been aborted when I try to open serial port

I have software that opens a serial port using C# and it does good with hardware com but with usb 2 serial com ports I get this error

the i/o operation has been aborted because of either a thread exist or an application request

I don't know what it means... although hyperterminal works very well at the same machine.

My code looks like this :

SerialPort.Open();

after initialization of course by the way my code work very will with Hardware Com Port !

thank you all it really helpful comments the problem was combination between WIndows xp and .Net framework 2 when i have upgraded to windows 7 with (default .Net frame work shipped with win7) which i think 3.5 every thing goes ok and my application work very will all other issues related to microsoft i but it between try catch block