So,
after hours of fiddeling and testing, i found the Problem.
my TC macro (M6Start) was based on an example from CSMIO.
at the end of the macro was the following code to anunce the new tool to the System:
SetCurrentTool( newtool )
Code("G43T" & newtool)
Code("G43H" & newtool)
i never thought about it
but the G43T.. caused the Problem.
so i started to get informations what G43T.. exactly does (or should do),
without any success.
so it is running now without this G43T..,and without knowing what is should do.
i can live with this.
TPS