Very slow packet writing with PX-712A

I just bought a PX-712A to replace my PX-2410TA.
When writing to a CD-RW with packet writing (InCD 4) this goes very slow: about 10 minutes to write about 34 MB of data! With my previous Plextor writer and also with my Lite-ON 48161H, this goes A LOT faster. The drive seems to write something (orange led) then pauzes for x seconds (green led), then writes again, etc… In between the drive seems to be spinning up over and over again?
I also wrote some CD-R’s and DVD+RW’s without any problems (and fast!).
Whether I format first (UDF 1.50 or higher) or use MRW (mount rainier), it doesn’t get any better.

  • I use the recommended Verbatim CD-RW’s (8x-10x)
  • I use the latest firmware (1.05) and InCD (4.3.0.5)
  • Ultra DMA mode 2 is enabled
  • The drive is master on the primary IDE (there’s no slave)

What more can I do/try?