Having burn failures and can't figure it out? Here's some things to check.

Firmware up to date on the drive? Check and see if it is.

In Nero open SmartStart and go to Tools (ToolKit in Nero 6) then InfoTool.   Pick the drive in the drop down.   In the drive tab there's a field for the current version.

Where do you see if there's a later version?

Check the manufacturer of the drives website - usually under support.
If the drive came with the pc then check the pc manufacturers site for an update.
You can also check the firmware page - forum.rpc1.org/dl_search.php  

What's firmware you ask?  

Firmware is the instructions for the drive - think of it as a sort of operating system.
One important thing firmware does is give the drive   the media codes for it to have the right read and write strategies.
If the media code for the manufacturer of the disc you are using is not in the firmware then the drive will use a generic write pattern.   Doesn't always mean a failure but can.

What brand of media are you using?

Not all media is created equal :)   And not all is compatible with all drives even if you have the latest firmware.
Check the drive manufacturer's site for what brand of media is recommended.  
Different media may just do the trick!

Even if the media worked before a new spindle may not. That's because the 'brand' name outsources to a manufacturer.   Example Memorex   DVD's can be made by Ricoh Japan, CMC, Ritek, Fuji, Prodisc, Moser Baer, MCC and several more.

Good ones that are usually listed for most drives are Verbatim and Taiyo Yuden - my personal fav's.

Verbatim's are made by MCC the majority of the time.   Taiyo Yuden is the actual manufacturer and can usually be found instore under the name of Sony, Fuji, Maxell etc but look for made in Japan.   Or they can usually be found on reputable online stores.

CDs now are more widely supported by cd/dvd drives.   They've been around much longer than DVDs.
 

How about the burn speed?

Try burning at half the rated speed of the media.   Like 16x at 8x.   Just because the media says it can be burned at 16x doesn't mean that that's the optimal burn speed.

 
All your drives in DMA Mode and not the slow PIO mode?

You can check this is device manager.   Right click on my computer >properties >hardware tab >device manager.
Click the + next to IDE ATA/ATAPI Controllers.

Both current transfer and transfer mode should have DMA listed.
If one of the devices shows Transfer Mode - Not Applicable - that's ok - just means no drive is connected to this channel.

 Program you're using to burn up to date?

Most CD/DVD burning programs are pretty stable and do a good job - esp. Nero :) but there may be a bug with the program and your pc setup that   an update will fix.   So keep your programs current.  

Well that's about it - just some basics.   Feel free to add what I might have missed!