7in1 drive keeps disappearing

I have a Mitsumi 7in1 with floppy internal drive in my computer. It works great for while but they the drives dissappear in My computer and the only way to get them back and the device working is to open the side of my case and unplugg and replug the usb cable in the usb card and winXP sp2 redetects and the drive and it works again. It did the same thing when the device was plugged into my motherboard USB too. Rebooting does not help. It always needs replugged in to work again.

I only have power settings that turn off monitor and hard disk, no hibernate or standby.

Comp Specs:
Asus motherboard
Athalon XP Processor
1gig ram
160gig SATA Segate HD
Geforce 5700 Ultra

Any ideas?

In device manager, under the power tab, uncheck the box that allows the computer to turn off the power to them.

That did it! Disabling the power managment on the USB root hub it was attached to kept the drives enabled.