USB key loses partitions

[ilm]

This isn't strictly related to only Gentoo, as this also occurs when using RH9 at uni.

Several times, I've been using a usb key when it suddenly dies on me. The device is still in /dev (i.e. sda or sdb), but not any partitions (e.g. sda1).

When taking it over to a Windows computer, it detects the drive but says it has zero capacity.

Most recently, it happened with a brand new usb key that I bought two days ago (Saturday). Since my laptop (running Gentoo) is being repaired (since Friday), I was using Windows XP on another computer I have at home, and it was working. I brought it into uni this morning, in a lab using RH (9 I think) and it was working for a while, before the same thing happened: the partitions died. I'd try fdisking it, but I don't have su priviliges here.

What's wrong??? Is it linux? I don't think it's the usb keys, since this new one is a different brand to what I've used before.