thx Mike! but I tried everything - with and without history. I did not change the geometry exept extracting - what in my opinion is an operation which for sure changes the number of components in an object.

BUT! when I woke up today a workaround came to my mind. did not try it yet but it WILL WORK! hehe.

duplicating - averaging vertices in problematic areas and flaten out the borders - dannyUV the obj.
then I simply do with the UVs in the set what I tried to do with the geometry before. -> split UVs where I before extracted the geometry. then convert the selection to UVs and voila -> move them away. se bon. this is going to be a very nice unwrapping. wheeee!

I found one german tutorial about the same method with maya 4.0 - nobody seems to face the same problem with extracting and transfer.