Unable to format or access DVD+RW

I am unable to format, partition or access in any way my blank DVD+RW 4.7G disk. I can see it in Disk Utility but all I can do is erase it. After this I am unable to partition or mount...

When I was 'playing' I might have selected 'Lock for editing' (Partition Tab), but this is no longer displayed.

Any Ideas ?

Mac convert after using Windows since 3.0 - It took 18 years to see the light !!!

My specs are below...

My MAC:

iMac G5 20" 2G (Machine Model PowerMac8,2) - latest mod

My SuperDrive (internal):

PIONEER DRD-RW DVR-K04L
CD-Write: -R, -RW
DVD-Write: -R, -RW, +R, +RW, +R DL

Media Being Used :

Media:
Media Type: DVD+RW
Blank: Yes
Erasable: Yes
Overwritable: Yes
Appendable: Yes

Info from Disk Utility:

Name : PIONEER DVD-RW DVR-K04L
Type : Disk

Disk Identifier : disk2
Media Name : PIONEER DVD-RW DVR-K04L Media
Media Type : DVDROM
Connection Bus : ATA
Connection Type : Internal
Connection ID : Device 0
Device Tree : uata/@0:0
Locked : Yes
Writable : No
Ejectable : Yes
Mac OS 9 Drivers Installed : No
DVDROM : Yes
Erasical Optical Media : Yes
Optical Media Type : DVD+RW
Device Type : CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD-RW, DVD+R, DVD+RW
Location : Internal
Total Capacity : 4.4 GB (4,700,372,992 Bytes)
S.M.A.R.T. Status : Not Supported
Disk Number : 2
Partition Number : 0