My first unit and it's first ride info is
here. I replaced that first unit, and the second. (Second was DOA out of box, looks like Best Buy stockers may have abused it).
My third unit does exactly what yours does. It a few times stopped playing mid song, and would resume minutes later. After the 4th time, it locked hard, and I just put it away since I had nothing to reset it. From what I can tell, the hard drive has issues with the vibrational forces felt on a motorcycle, and will go into a state of non functioning for a few minutes, or sometimes until it is powered off. The vibrational sensitivity seems to be much worse then a normal 2.5 inch disk. I knew a rider with a Creative unit that had a 2.5 inch disk, and he never had an issue like this on it.
My
poll on Riovolution seems to be mixed. For several, it works fine. But for 2 in the poll, they report complete lockups, but didn't bother posting about it.
Unfortunatly at this point I am looking into an iPod. I'm going to see if I can borrow my friends second generation unit and see if those hard drives have similar issues. For me, a portable player is rarley going to be used outside of my motorcycle rides, so I may have a new Karma with a 3 year warranty up for sale soon.