Unable to burn Multisession DVDs

While burning DVDs the option for “Adding files later” and “Write Method” is grayed out in Nero as shown below. How can I select the write method (SAO, TAO) and burn multisession discs? Can I still add some data to the disc (shown in the image) that has been finalized?

DVD-Recorder : BenQ DW1655
Firmware : BCHB->BCIB
Burning S/W: Nero 6.6.0.13
Dics Burned : Writex 1X-16X DVD-R
MoserBaer 1X-16X DVD-R

Write Method:
http://img216.imageshack.us/img216/2469/extendedsettingsxd9.th.jpg

Allow Files to be added later option:
http://img216.imageshack.us/img216/3143/multisessionbx2.th.jpg

I am not too sure about this … but .. I see from the picture you are making a bootable DVD … maybe that is the reason Multisession is grayed out.

Thanks Eazy
I checked it out. The DVDs that I burned were DVD videos and a bootable DVD. When you burn a DVD video or a Bootable DVD, the disc is finalized. The option to add files later is available when you burn DVD data.
However even upon burning a data DVD the option to select the Writing Method is set at ‘Disc at once’ and greyed out as shown below. Doesn’t Track at once utilise the space more optimally? Does it matter much or should I just keep on burning as such?

Change to DAO.. it’s more efficient, as when you use TAO, each session requires space for a lead-in and lead-out.

I’d suggest a complete reinstall of Nero. Try that first, else switch to a different burning app.

“Change to DAO.. it’s more efficient, as when you use TAO, each session requires space for a lead-in and lead-out.”

Did you mean change to SAO as its already set at DAO (Ref.: The pic in the thread) with no option to change it.
I’ll try reinstalling Nero and see what happens.