@Piru,
It could be the Power Flyer :-( The problem is, i can seem to listen to mp3 or play games on HD for an hour or so, then all hell breaks loose. I get that error message and then it freezes. Meaning a reboot, and i even get the error message on startup. Meaning another reboot. Sometimes, i would have to leave the damn thing off for 5 mins for it to reboot again. I don't think it would be a good idea to boot up Hard Drive without Power Flyer, as its 30gig. Oh yeah, i forgot. I also have a "spare" 1.7gig Hard Drive, and i also get checksum errors on that as well.
In other words, sometimes it would be working, then out of the blue all hell would break loose. To be honest, i don't know what's wrong. I thought it was Hard Drive, A1200 mobo, Power Flyer, RAM and even my PPC Accelerator!
It doesn't sound to good.
-edit-
The Power Flyer is also firmly strapped into place via the plastic clamp.