Ghost External HDDFollow

When you restart the computer, does the drive and all it's contents work correctly, or are the files gone even after that?

One possibility can be drive letter mapping. if you had a USB drive assigned to a specific drive letter, say G:\ and hardcoded in the format that way, but later take it out of the system and plug in another USB drive that happens to also get assigned G:\ because of number of drives in the system, then the hardcoded one won't appear at all when you plug it back in until you set it to a different drive letter. those 60 in 1 card reader thingies are notorious for causing that because they still show up as a drive letter even with no media in them. HP printers often include them built in, so it might be something to look at. That doesn't entirely sound like what is going on in this case though.

Usually when drives start behaving "iffy" like that, it means that the controller in the actual USB stick itself is starting to go bad. Thats usually confined to a specific drive though. What you might possibly be running into is static discharge. do you have a metal keyboard tray or metal desk that would likely accumulate a large static charge at any time, and do you use a corded mouse? The old IBM optical mice were especially horrible about that. they would conduct a charge right back to the usb ports due to crappy design, and knock them out temporarily, eventually frying the USB controller.

Another possibility is the motherboard. sometimes, especially on nvidia controller based motherboards, the southbridge chipset connections just start destabilizing as they age. Best theory as to why I have heared is that there is an onboard low level 16kb flash cache associated with the chipset, and it starts to degrade over time. If you have a Nvidia chipset board that might be the cause.

Other things of potential concern would be undervolting, especially if you have a higher end video card and too many internal drives. external powered usb hub is a temporary fix for that, better PSU in the computer for a permanent fix.

Or it could be the OS. windows does odd things with its USB stack sometimes. factors that can agrivate that are certian specific USB perephrials, such as a logitech G-15 keyboard on an intel 1366 chipset bus.

If any of the sticks are OCZ, then its probably the memory stick's fault since OCZ makes crappy memory sticks.