Hey all, I joined specifically so that I could tell you about how I went about fixing this in my Clip+.
I had had my Clip+ for about a year and a half when this started happening. At first the jack was intermittent but not very wobbly and it still worked with some cables but not others so I thought that my cables were faulty. Then it got very loose and started being intermittent with everything I used.
When I opened it up, I noticed that the same soldering point that the OP noticed was broken, so I soldered it and figured that would be the end of it. However, that turned out to not be the only thing that was causing my troubles. The jack was still moving around independent of the contacts (meaning that the plastic part that actually holds the audio cable was wiggling but the contacts weren't), causing the intermittent signal I considered using hot glue, but I didn't want to do that because it would be a pain to get off if there was trouble later on. So this is what I ended up doing:
Huddler (the most annoying forum software on earth) was having trouble embedding images, so I just linked to them on imageshack instead. Sorry.
1) I cut a strip out of an old sock that was in my rag pile that was approximately the width of the jack and about twice as long as it was wide.
http://img203.imageshack.us/img203/8171/img6437w.jpg
2) I then folded it in half, placed it on top of the jack, and wedged it in between the jack and the battery using my jeweler's screwdriver (making sure that the strip of fabric did not extend beyond the outside of the jack, as it would be in the way of the audio cable).
http://img152.imageshack.us/img152/1849/img6441rd.jpg
3) Then I put the thing back together. As I had planned and indeed hoped, the added pressure from the sock holds the jack very tightly in place and does not allow for any movement whatsoever. The headphone cable doesn't even spin freely in the jack anymore.
http://img121.imageshack.us/img121/3176/img6444x.jpg
Anyway, I hope that this was helpful to people who either don't have access to hot glue/superglue or, like me, want something that is simpler and less likely to fail again in the future.