Problem in accessing the COM port. "Access denied for COM1 "

[C# Programming]

I have a hardware connected to the usb which communicates by sending the data.When i will start the application and hardware as a fresh it will work fine.But when i will stop my hardware and run it again it will throw me a exception handle stating that the Access denied for COM1: as you dont have proper rights to the resource.But when i remove the USB plug and re connects my application to the hardware it will start working.
Do anyone know how to reset or re intiallize or reconnect the usb to hardware programitically...?