Burning Speed of 16x Superdrive suddenly slow.

I forgot which day, but one day a couple or so months ago my superdive suddenly slowed down. I used to be able to burn at a maximum of 16x (DVD-R's), but whenever I try to burn these days, I can only get 2x speed maximum.

I tried two types of disks. I forgot one of the types (as I borrowed it from a friend), but I think it might have been a Maxwell DVD-R. The ones I normally use are TDK DVD-R's. Both types are 16x maximum speed. I had previously burned the TDK's with 16x speed.

Also, Toast Titanium (fully updated to 7.1.2) initially (with no disc in the drive) displays multiple speeds all the way up to 16x. Once the disc(s) are inserted, it goes to 2x, regardless of either type of disc. Then the burning also takes longer than it used to take.

Apple System Profiler:

HL-DT-ST DVD-RW GWA-4082B:

Firmware Revision: C03D
Interconnect: ATAPI
Burn Support: Yes (Apple Shipped/Supported)
Cache: 2048 KB
Reads DVD: Yes
CD-Write: -R, -RW
DVD-Write: -R, -RW, +R, +RW
Burn Underrun Protection CD: Yes
Burn Underrun Protection DVD: Yes
Write Strategies: CD-TAO, CD-SAO, CD-Raw, DVD-DAO
Media:
Media Type: DVD-R
Blank: Yes
Erasable: No
Overwritable: Yes
Appendable: Yes