I see you tried a "reset" but if you didn't try resetting network settings, try that.
Tap Settings > General > Reset > Reset Network Settings
Then restart the device.
Hold the power button until "slide to power off" appears. Slide to power off. After it is off, press the power button to turn it back on.
I had this problem as well. Tapping the pause/unpause button didn't work. What I did to fix it was to go run the music app, scroll down to the song that was causing the error and tap on it. The song had an icon indicating that it was downloading or something. When I clicked on it, at first it brought it up along with the artwork. I hit back, clicked a few more times on it, same thing. Then I clicked on that icon I just mentioned and the song disappeared. Went back to iTunes on my phone and noticed that it was no longer stuck pending! Redownloading then worked. This was on an iPhone 5 running iOS 6.