bulia byak <buliabyak@...155...> schrieb am 09.12.2009 19:39:55:

>It is worth submitting a bug, if you attach such a complex
> drawing and detailed steps to reproduce, as well as information on
> your OS and hardware.
>

Thx for answering bulia byak! But I think it is not necessary any more.

I also posted this mail to the Inkscape Forum. A user suggested to change the mouse settings under "Preferences".
This morning I started to work with a another complex model plus my tablet (mouse settings unchanged). It startet off fine.
However over the time the movements with my tablet pen on canvas got slower and slower. Also after restarting. Just as mentioned in my previous mail.
Only then I changed the mouse settings in preferences as suggested by the inkcape user and restarted.  
And volia! it seems to be the trick! Tablet pen behaved fine again. I looks very promising.
Although I have to do furhter testing to really confirm this.