USB Disks Ejecting Themselves.

I'm about at my wit's end here, so very much hoping someone here will be able to help me out...

As of this morning, whenever I plug a USB drive (be it an external harddrive, pen drive, or even my iPod) into my MBP, it runs without any trouble for between three and twenty minutes, then ejects itself, with the warning that it was 'not ejected properly'.

I googled the problem, and what minimal answers I found recommend I deactivate the energy settings' function to automatically sleep disks where possible. Having tried this, and rebooted twice, I'm finding the exact same problem with both settings.

Any advice? Is this happening for anyone else? Is there potentially a problem with my machine / USB ports? Any advice (notwithstanding "deactive 'automatically sleep disks in energy settings'") would be appreciated.