With media not in the drive, no. It should then increase the max speed back to 48x. Try disabling Smartburn though, as cfitz says, then re-enable it because it might just be something in the system getting confused.
As for the Princo 48x media, it's highly likely that the LiteOn sees this media as 40x only -- remember the drive doesn't read the max speed from the disc itself directly, it simply has a database of media types and their maximum burn speed in its firmware, and such a system is not always 100% accurate. Grab hold of some CMC, Prodisc, Ritek etc media and the figure should go back up.
Trust us, the problem is 99% certainly down to Smartburn in some way or another. Count yourself lucky you don't have an MSI 48x -- good as this writer is for the money (and it is canny enough) it only sees 48x Princo media as 16x. D'oh!