Pioneer drives only write at 2X on media that Pioneer has certified. This media apparently wasn't certified by them.
A workaround is to apply a patched version of the firmware that has this limitation removed and will allow you to attempt a 2x write on any DVD-R media. You can get the patched firmware at:
Some other useful sites for Pioneer DVD-R drive info are:
I'd suggest reading the forums before you attempt to flash. There is supposedly a bug with the 2x patched 1.40 firmware that will cause it to ruin CDRW discs. Also, if your drive has (I think) 1.32 or above from the factory, it won't work with an earlier version. And it is possible to destroy your drive when flashing the firmware.
Anyway, with the 2x4all patched 1.20 firmware, I am able to write the Princo white-top 1x discs I got from allmediaoutlet.com at 2x with no problems.
If your discs seem to be working ok for 1x but you apply the patch and they don't work at 2x, you should be able to flash back to the original firmware or just select 1x to write them (as long as you're not using the patched 1.40 firmware which supposedly always writes at 2x no mater what you select).
I've been using the Princos at 1X for about 6 months and just got around to flashing the patched firmware. I'm glad I did as it doesn't seem to lower the quality at all, but cuts burn time to a half hour.
(Hmm...now we have a half-media, half-firmware post...)