This is the exact same problem I had with my Sansa m230, and the entire reason I bought the clip.
Over time, the headphone jack seems to lose connection, and you get crackling over the headphones. It gets worse and worse, until you either get one channel, or you have to hold your finger against the jack to make a good connection.
With my m230, it this started after around a year, and took another 6 months before it was unusable. With my clip, it’s maybe 3 months old, and it’s well past the point where I gave up on the 230.
I love Sandisk products, I just wish they’d make the headphone jack a little more robust. I’ve never had this sort of thing with any other player.
Fortunately, the manager at Best Buy offered to swap mine for a new one. Hopefully this one will last a little longer.
Anyone else with a dead or crackling headphone jack?