Erin:
A new firmware was released late last month; here is the
download link. I don't remember if you need to copy the file to a floppy disk or if you can just run the .exe from Windows. I would try running in Windows first (you may receive a warning message box if it doesn't permit you to run the .exe via Windows; if this is the case, you'll need to have a floppy disk handy).
If the firmware update doesn't work, it's possible that the laser unit may be poorly calibrated when it left the factory and you may need to RMA it (
link). DVD+/-RW drives are fairly inexpensive to replace, so you may need to weigh the pros & cons of an RMA vs. purchasing a new drive. The SHW-1635S was one of Lite-On's better DVD writers; it's possible that you were unlucky with this particular unit.