Thanks DTanis, your suggestion worked.
After having backed up some .cfg files, dictionary's and logo's in /system dir, and placing FW 2.1.2 with fast display driver in the root of external memory, I did a format.
Within a few minutes I got a brandnew system back.
However, the issue I had which made me do this format still exists.... :-(
Anyway, I 'll update the other post which described that issue with further notes.