MEGA2560 USB-driver stops working on Win XP

I have an application that sends data to my PC and is suposed to run all the time. The problem is that the application lose contact with the serial port after 10 to 20 hours. My first thought was that there was a error in my PC app so i wrote a new one (first Processing then Delphi), but with the same result.

When i try to restart the application it can't open the serial port and i have to restart the computer to make it work again.

Has anyone experienced a similar problem and have a solution?

Hardware/software
Arduino ADK
Windows XP
Standard Arduino USB driver

/Magnus