Gallbladder problems like pain and discomfort are often caused by gallstones. Gallstones are solid pieces that are usually made up from cholesterol and bile. By blocking various ducts, they can cause nausea, vomiting, yellowing of the skin, as well as major pain in the abdomen and further up into the back or even arm. In many cases however, the gallstones will be asymptomatic (without symptoms).
Every year more than a million Americans are diagnosed with gallstones, so you're not alone. About 700,000 of those million will have to have their gall bladder surgically removed.
I have not come across any specific diets/foods to *treat* gallbladder problems, but I can tell you what has been found to prevent them - which to me logically would help if you already have gallbladder problems. However, before I do that I'll just mention that it's important to get checked out if you think you may have gallbladder problems as they can be *life threatening*.
So, to reduce your chances of developing these gallstones, it is best to follow a diet of fresh fruits, vegetables, whole grains, legumes and nuts; and low in high-cholesterol, high-fat foods.[3,4] It has been found that on average vegetarians are up to 9 times less likely to develop gallstones than non-vegetarians. The Mayo Clinic suggest opting for high fibre diets that include healthy fats and potentially supplementing with vitamins C, E and calcium if you are not getting enough of it in your diet already.
If you are overweight, then losing weight can also reduce you risk of developing gallstones, however try to aim for slow and steady weight loss rather that speedy weight loss. This is because hasty weight loss can actually increase your risk of gallstones. There are also some medications that can increase your risk of gallstones, so speak to your doctor/pharmacist if you think you have gall stones, or are trying to prevent them. 
 University of Maryland Medical Centre, Gallstones and Gallbladder Disease
 Nutritionfacts.org, Cholesterol Gallstones
 Mayo Clinic, Gallstones: Alternative Treatment
 Mayo Clinic, Gallstones: Risk Factors