We have a Windows Server 2000 SP4 server with a StarTech 4-Port USB/PCI card (ALi chip). USB ports work properly. When *any* USB disk is connected, Windows' Disk Management recognizes it without a problem (name, size, model, files system, and says "healthy"), but in Windows Explorer, the disk cannot be accessed. In Explorer, when it appears at all, it will appear as a disk icon with a red question mark on it, and no drive letter, name or contents display. Clicking it gives "G:\ is not accessible. The folder was moved or removed."
We've confirmed that the latest drivers are installed for the USB card, correct driver is installed for the most recently-tried USB disk (Western Digital My Passport); and correct versions of disk.inf and usbstor.inf are installed. Device manager displays no problems; "USB Mass Storage Device" appears under USB Controllers, and the USB disk is correctly identified under Disk Drives. We've tried USB disks with both NTFS and FAT32 files systems, different size disks (down to 60GB).... In all cases, Device Manager and Disk Management recognize the attached USB disk flawlessly, but in Explorer the disk can't be accessed. Anyone got any ideas?