HIS Radeon 5850 fan noise (slipped bearing?)

I've been running my PC rig with a Radeon 5850 from HIS for the past few years, and it's been very good to me over that time.
http://www.techspot.com/review/206-his-radeon-hd-5850/

However, over the last couple of weeks I've had the card's built-in fan start making a very loud grinding noise when it's running, sometimes just when displaying the desktop. It seems to happen more often during gaming or watching video, and it's quite distracting in any event. It's intermittent, sometimes the PC runs completely silently, but when it starts making the noise it usually keeps going until I put it in Sleep mode.
I've checked all other components, nothing is contacting the fan when it spins, and manually stopping the fan (read: holding it still with my hand) completely stops the noise.

I've taken it out and air-blasted whatever dust I could get out of it, to no avail.
There's no easy way to expose the fan bearings (there's no apeture under the brand sticker, I checked), I haven't sprayed any lubricant in there as of yet.
The fan seems to have two positions on its spindle (axle?), as in I can push it in and pull it out about half a centimetre by hand - I'm not sure whether this is means it's damaged or whether that's just part of the design.

If anyone has any insight as to what I should do, whether there's a way of lubricating or fixing the fan or whether I need to think about replacing it, please let me know.

EDIT: Well, this thread has gotten to the point of notifying me that it's no longer active, so in the vain hope that someone who has knowledge of this topic will browse the forums in the next day or two, I'll add this paragraph and (hopefully) bump the thread.