A couple of things:
A) Download Lite-On's Smartburn program and see what it says your media
is rated for. I've seen discs with from the same manufactor with no
visible differences; yet one was a CMC 32x one a TY 40x...
B) Try nero.
I've had my 48x12x48x take over 6 minutes to burn a disc; and nero was reporting it was doing it at 40x!! A reboot solved that, though. Still have no
idea what caused it.
If you have an Intel based mobo, try install the IAA...