Problems burning CD/DVD's since 10.5 upgrade

Although it would be helpful to know your computer/version/and so on, we can proceed by posing some questions:
1. Does your computer require a firmware update?
2. Are the burn problems congruent with the 10.5 update? Could you burn before or after the update?
3. Have you performed all the diagnostics? (permissions repair via Disk Utility, Cleaning, PRAM, etc.)

OK, some questions:

1. Which OS version; 10.5 or 10.5.1?
2. When you installed 10.5, did you Upgrade or Archive & Install? And which version did you come from? If you have 10.5.1, did you use Software Update, or download and manually apply it?
3. Which versions of Toast & iTunes?
4. Open System Profiler in the Utilities folder. What does it say about your device & disc burning?

To Clean & zap your PRAM, start your Mac. As soon as you hear the chime, hold down the Command, Option, P, R keys (apple-alt-P-R). Your Mac will chime again. Keep holding them until your Mac has chimed 3 times, then release them. Hold down the Shift key. This will make your Mac boot in Safe Mode, which performs several housekeeping tasks as it boots. Your boot time will be longer because of this.

Once it's booted, try burning a disc from Disk Utility or the Finder.

Same problems here. MATSHITADVD-R UJ-857 on MacBook Pro, OS 10.5.1. Can't burn CD or DVD with Disk Utility or Toast.

I could burn before updating to 10.5.1.

Apple please fix this ASAP!

Try resetting PRAM and Safe Boot as described above.
Reapply 10.5.1 update (not the one from Software Update, but the 110MB download version).

Then run Disk Utility while booted from your startup drive and Repair Permissions (it will take longer than expected, but that is a different issue, known, and not a problem in this context).

Are you using the most recent version of Toast? Earlier versions are problematic in Leopard.

Same thing here...
MacBook Pro, running 10.5.1 and Toast 8! As soon as I got Leopard I had burning problems wit it taking hours and hours to burn a single 4.4GB DVD. Upgraded my Toast to Toast 8 and it still does the same thing... what was taking 15 to 30 minutes is now taking a few hours.... not just a couple either.... 4 or 5. I tried a different software and it is doing the same thing.... leads me to believe it is a system software issue.... Drive is the built in MATSHITA DVD-R UJ-857

I have also zapped PRAM, Repaired permissions, ran Leopard cache cleaner, etc....

Still burning sllllooooooooooooowwwwwwwwwwwwwwwwwwww