First thing, check to see if your program has been inadvertently set to make a DVD when you've got only a cd burner connected, or some such thing.

Next, make sure that the device you intend to use is actually a burner and not simply a cd or dvd player.

Next, check to see what devices your program is aware of, Toast Titanium has a pull down menu under "RECORDER" where you can find that info-

Somewhere in here, check to make sure the recorder/burner doesn't have a recorded disk in it, and that you are not trying to burn a copy of it(A dumb mistake, yes, but it can happen, and it does happen).

Now, check to make sure you have a driver for the device you are trying to burn to--if not, and maybe even if so, go to the mfg website and look for the latest updated driver. Even if you bought the burner yesterday, it is quite possible that there is a updated driver that will fix your problem.

Somewhere in the mix, you should try burning from another program, and also check for updates of the program your using.

When you can't think of anything else, connect the burner to another computer and see if you can burn from it. If you can't, it maybe time to order a new one.