Sound like a problem with Windows. Disabling/Enabling usb makes windows rediscover the USB interface again. Do you run with any powersave or sleep mode enabled? Think there’s also some kind of powersave on USB. Have you tried running with another PC?
My uptime on a windows-server is generally 1-2 months after which I normally reboot due to some windows update. Uptime on my NAS is kind of unlimited 🙂
Btw, sorry for the edits above, messages are as original, but I have some problems with my new forum setup wrt language setup and posts get messed up.