Thanks for your attention, Ssseth!
Just this evening I've found the "solution": it's not related to media as I thought first like you. I use Verbatim US-CDRW which are good quality media. Memorex I only used for crosschecking and I knew before that they are bad quality.
The reason is --- firmware!
With LDW-451S GSB7 UltraSpeed CDRW is only burnt at 16 CLV:
With GSB6 the drive behaves as it should:
Also with GSB6 the CDRW media is logged in faster and without much head moving.
So much about "in GSB7 we only changed Booktype Setting"...
Tomorrow evening I will check with 851S firmware versions, but I expect the same. Either "Booktype Setting" or "24speed with CD-RW media". Liteon, this is BAD!!!