It is not always true that the burn speeds MCSE shows for a certain type of media is the speed the drive will burn it at. I've run into two cases where a certain LG writer (different model from your drive) seems to have some kind of speed lock in the firmware for burning certain kinds of media. MCSE shows that they can burn at a certain speed but when you try, only a lower speed is allowed.
I'd suggest first trying Geno's suggestion, but boot into safe mode first and then flash. It is possible to have a flash which did not quite proceeed properly. Reflashing in safe mode is the usual recommended cure. The usual cause of an improper flash is a conflict with some kind of driver or other. Booting into safe mode usually ensures most third party drivers are not loaded.
Next, try with some other media and see if you experience the same problems. It could be a case of a firmware lock as I mentioned above. In any case, there are lots of complaints about RITEKG05. Have a look in the media section. Quite a few people have had experiences where the discs burn fine, but they become unreadable a few months later. Hence chef's "crap media anyway" comment.
If you find that with other types of media, the same odd problem rears its head, then it's time to do some diagnostics. Put a DVD disc which already has something burned on it into your writer. Then do a burst rate test with Nero CD Speed and see what you get. Something around 22MB/s or more is good. Anything less means the drive isn't receiving data fast enough to do a burn at a decent speed.