Thank you teedub, I was going to send the clip+ back until I saw your advice. Just to confirm what teedub said (and to assuage any fears of damaging the device!) you do need to push the headphones very firmly into the device until you hear a click.
Got a Sansa Clip 2G last week and the headset connection was intermittent out of the box. I had to fiddle with it to get it to work but the slightest movement caused it to lose contact. Checking on line I saw that this problem has been reported for 3 years. It is incomprehensible that SanDisk has not corrected the problem and that reputable brick and mortar and on-line retailers continue to distribute it. I ordered a replacement because other than this critical problem the device's functionality and performance is excellent.
as of 8/2011, the Clip Plus headphone jack doesn't last more than a few months, either. Just got an RMA and am returning mine for warranty replacement. I only take the the headphones out of the jack when I charge it, which is probably about once a week. As this thread is several years old, it doesn't appear that Sansa cares too much about this issue. Make sure to spread the word. Maybe a drop in sales or enough bad publicity might make a difference.
After 15 months of light use, mine also started breaking up if there is any movement while the phones are plugged in. I have had to remove the phones after each use as the clip broke very quickly and I am now going though a belt loop to secure it. Battery charge life also dropped considerably pretty quickly. Despite all of this, I love it and will probably order a replacement. I use it at home with high quality Sennheiser headphones - Truly amazing sound quality and selection of music from about 1000 songs (almost completey used up 8GB).
I've never had any problems with the headphone jack, but then I never ever even tried the horse-suppository-sized ear buds that came with the player. Never mind that they look really cheap (which may be the reason why some people are experiencing problems with their headphones) but since my ear canals are not the size of horse suppositories, I bought a soft pair of JVC ear buds at the same time I bought the player.
When I later bought a Sansa Clip player for my wife, I bought her a soft pair of JVC ear buds to use with it, and neither of us has ever had any problems with the headphone jack.
i've had issues w/ my first sansa clip+'s headphone jack. repeated insertion/removal of the headphones over a period of time (less than a year) will loosen the fitting. so i recommend that you keep your headphones plugged in at all times and remove them from the player only when necessary.
I have two sansa mp3's. I always loved it so when the first started having earphone problems, I ordered a new sansa fuse. That one immediately had a problem with getting stuck in pause and I should have sent it back because it never got better. Now, I have the same problem on the sansa fuse with the earphone piece, ie, not being able to hear out of both ears at the same time no matter how many different earphones I tried. I called Sansa troubleshooter who asked a lot of questions and then disconnected me when he found out they were out of warranty. I am really disgusted and will never buy another Sansa. ***Since posting this, I was contacted by a Sansa mgr who was able to send me a replacement. I have been using it for a few months now and have no trouble. I keep the headphones in all the time which I think and hope may be the solution as I used to remove them whenever I wasnt using it. As I said, the sound is great and I love it when it works.