DVD Burn Failure

I am having problem writing a DVD+R with data files using Nero 6.6.0.18, in a 7 month old Philips DVD +/-R/RW Drive.
It finishes burn successfully, but then fails to read or acknowledge presence of DVD after re-insertion. This has now happened 3 times consecutively.
The drive still reads, rips audio CDs, haven't tried buring a CD-R yet?
I am using Logik DVD+R suitable for x8, and burning at x8.
Have already burned ~30 of this 50 pack, and previously 25 of another brand.

Can anyone suggest what the problem may be, and hence a solution?
How can I determine if my drive is/is not working satisfactorily without using up valuable discs?