What operating system do you have? Do you have Nero? Is your LG an external? Did you update your motherboard utilities before that started? Those can screw up burners, on random systems - If you're running Microsoft, you'd switch to their drive controller drivers.
If you have Nero, you can check out your system with Nero Tools. If not, and your OS is compatible with Nero, then I'm positive that you can get the Nero tools on a free download somewhere, or you might have something analagous with your own burner software.
You could check your ASPI layer with ASPICheck. If I recall, there are alternative drivers for external...
My memory isn't very clear on these topics, and I won't have a chance to search out specifics. But CD Freaks forum is the best place to look for answers.