Mapped drives “x”ed out

I’m having a problem with some of my WinXPro machines where the user’s network drives are all shown with the red X in Explorer but can be accessed once the user clicks on the drive. Normally, this would not be a problem, but some programs are acting as if the drives are not present due to the red X. Once the user clicks on the drive, the program in question then recognizes it. any help???