Oh it's definitely an issue. Mine is awful. One turn of the knob will send the volume up around 20 steps or so and down as much as 30 or 40. It can jump from volume 50 to 75 or all the way down to less than 10 with one turn of the knob. Yesterday at work I was listening at volume 50 with my K3003's on and I turned the knob one turn and it shot all the way to max 75. My ears are still ringing. I just about threw the AK240 across the room. I have to send it back to Vinnie since I had the RW mod done and he is nice enough to look into the problem to see if there is anything he can do. The only solution is to pause the music everytime before you adjust the volume so when it jumps way up you won't go deaf and then unpause the music once you get the volume correct. And I can attest to the fact that it has nothing at all to do with swiping on the screen; I am extremely careful when I adjust the volume as to try to avoid this and my fingers are nowhere near the screen. It is a faulty volume pot iRiver used. And I also emailed iRiver months ago about this and received the same standard response that it would be addressed in a future firmware update. All updates since have not had any effect on the problem.
I am in the same situation, but the problem is not too bad...so let me know how it goes with Vinnie.
Sorry to hear this problem that you have and hope you'd find a fix very soon. Take care