Originally Posted by Random11

I have some sympathy with the OP here. I recently had four flats in four weeks, with no obvious problem with the tire. I even took the tire and rim to my LBS, thinking they might spot a problem I couldn't find, but they said everything looks fine and put another tube in, which I did, and I had another flat. I replaced the tire 11 days ago (I had an extra tire at home) and it's holding air. Apparently, there was something wrong with the tire that neither I nor my LBS could find

Given the OP's problem, I'd try to inflate a new tube before putting it in the tire. Just pump some air in the tube to see if it will inflate. If it does, the problem is not with the tube or the pump. If it doesn't, the problem is either the tube or the pump (but if it is a new tube, probably the pump)..