Windows 7 - USB stick - No drive letter allocated

Bought 3 Sandisk 2GB USB sticks for using on a floppy disc emulator. The emulator software effectively divides the USB stick into 100 virtual floppy discs. This I did on the first stick on my Windows 7 PC, where the USB stick was E drive, then I did something wrong (probably removed without 'ejecting') and all of a sudden the Windows 7 PC is not seeing the USB stick.
Disk Management within Computer Management sees the stick but when I try to allocate a drive letter I get the message "the operation has failed because Disk management view is not up to date......" refreshing & restarting as instructed does nothing. Trying it in safe mode is no different.

On my XP laptop the stick is seen OK and accepts files. the only difference I can see between the offending USB stick and another identical one is that there is 512 bytes allocated on the stick the Windows 7 PC sees whereas the offending stick is fully unallocated when reformatted (FAT).

I know its only a cheap USB stick but it must be something simple and I dont want to be defeated by the little so and so.

Any thoughts?

have you tried simply reformatting the stick on the xp machine and assigning a letter there?
you really should be using fat32 anyhow, compatibility is much better for fat32.

In fact I'm not entirely certain win 7 supports the ancient standard fat table.

Yes. Tried formatting the rogue stick on the XP machine and it behaves (to me) normally - XP m/c sees it straight away, can format it, can transfer files to it, etc.
The sister stick is FAT and can be seen on both machines.
Putting the offending disk, reformatted FAT, in Windows 7 machine and its still not visible in explorer, but is in disk management, but cannot be allocated a drive letter.
Only difference I can see between the sticks (looking on the XP machine) is the 512 byte allocated on the sister stick.

Probably a long shot, but try formatting it as NTFS.