What Happened?

I decided to ride to work to see how long it would take. I put the "new wheel"- an old fixed wheel that I unfixed. Of course, I forgot that I still needed to redish and respace it, since it was now 8-speed. I somehow managed to do that without all my tools. While I was at it I replaced the front brakes (that lasted approximately 2 months in this weather). I had a smooth ride to work- all 15 minutes of it- almost all downhill from home. When the road turned up a little, I kept dropping the chain- this time up front. I no longer have the cog with missing teeth in the rear- but I still couldn't keep my chain on. It fell off at least a dozen times on the way home. At this point, I noticed I had a bent chainring. I have no idea how I could have managed to mangle a 42t ring. It looks like I will have a project this afternoon.