I had a similar problem that ended up being the chain. It would be best anyway for you to replace the chain if you are wanting a reliable commuter bike. Replace it with a compatible Sram (or other brand) chain that has a quick link for easy removal.
What happened with my bike was one of the links had a piece that wasn't milled correctly and was sticking every so often. It was a lot of trouble to pin point the problem. I adjusted the all of the parts that I could, cleaned and oiled the chain on a daily basis, and even disassembled the rear cassette, but the problem kept occurring. In fact, I couldn't find the exact reason until I popped off the sticky link (after several months of jumping, clanking, and everything else, it finally stuck) to slip in a quick link.
Even if you don't think that it is the chain, it might be best just to swap it out for a new one with a quick link. It would help you to eliminate one variable and also give you a new reliable part that can be easily removed for cleaning and re-oiling when needed.