[Dadx2mj]

These kinds of issues can drive a person nuts because we dont know if the issue lies with Castle Link, Win XP , or some other application on the computer running in the back ground. Sounds to me like you have covered the probable issues with Castle Link so maybe start looking at things with the computer itself. Maybe try disabling back ground apps like firewalls or virus protection or any unnecessary services that might be causing conflict running in the background. Another option would be to do a repair operation of Win XP itself.