Sansa Clip freezing - not recognised by PC

Hi everyone - first of all, thanks in advance for looking at my problem… I’ve had my 2GB Sansa Clip for a couple of years now, and I’ve never had any real problems with it (at least, none I couldn’t easily solve myself). Today, though, it’s started playing silly buggers for no reason, and I can’t work out how to get it back on track. When I turn it on, it freezes at the flower screen for two or three minutes, then goes to the “refreshing media” page. The bar fills up relatively quickly, then it freezes at full bar for another few minutes. After this, it goes to the “Goodbye” screen, freezes there for a couple of minutes, and turns off. All without me doing anything. When I hook it up to my computer, I get a “USB device not recognised” message. If I leave it connected for long enough (5 mins), it will eventually be detected, and Windows (I use Windows 7) will ask if I want to check the drive for errors. Whether I do or don’t doesn’t seem to make any difference. I can then navigate through the folders on the Clip, but any time I try to do anything (delete the one file that’s on there, which doesn’t seem to be corrupted as the version on my computer plays fine on WMP, reformat the disc, etc) I just get an error message saying that Windows can’t read the source disc. I’ve already read through a ton of similar posts on here and tried everything suggested, but nothing works. I’ve tried holding down the middle button when plugging it in and trying to restart the player by holding up the on button all the way through the freezing cycle described above, but all to no avail. If anyone could help me out with this I’d be hugely grateful, as I use my Clip every day and really don’t want to have to buy a new one unless I absolutely have to. Thanks again for reading this.