Tracks won't arm for recording

I was playing around with my Sony Acid music DAW, and inadvertently did something to cause to cause the "arm for record" button to turn pale. It won't come back to its normal look and I cannot get any recording done at all. Obviously my fault. Any help. I'm stuck as of now. Don't know what to do
The audio device is Microsoft Sound Mapper. I do not have an external PC interface connected at this point. But before a few minutes ago, at Sound Mapper, I could easily record. Earlier I was messing around with Reaper which is also a DAW on my computer and that would not record either.
I'm glad that solved it.

One thing I sometimes do in Vegas Pro is to switch to a different audio device type, click Apply, then switch back. In Reaper you might try changing to a different audio system (Options -> Preferences -> Audio -> Device -> Audio system dropdown menu, click Apply) then switch back. It might save you the trouble of rebooting.