Hi, I have a similar problem:
1st PX-716A TLA0202 (Nov 2004), media YUDEN000 T02 (Verbatim DVD+R 8x Pastel Slim-5x, Reorder #43464) written in Jan-Feb'05 at 8x with latest Nero and curently latest FW: ALL Plextools tests was OK, incl. TA (good and very good) but... the drive was very noisy and vibe and RMA-ed
2nd PX-716A TLA0304 (Feb 2005), same media (from same package!) written at same 8x with same Nero version: ALL Plextools tests, EXCEPT TA, are OK:
SUM8 PIE: Avg 0.12, Max 9, Total 15896
SUM1 PIF: Avg 0.01, Max 2, Total 713
TA Test: Not Good-Not Good-Not Good
Same results with FW 04, 04u, 05, 06 and latest Nero. I re-check my old burned dvd's (on 1st 716a) - TA is good and very good! In both cases PC-configuration is same, 716a is master on 2nd chanell (as slave is Premium), DMA is on, standard MS IDE driver, 80-pin cable (original from retail package).
P.S. Sorry for my english, this is my 1st post in this GREAT forum