I've got the failure:
It's caused by the windows options.
System Controls Menu/ Mouse Options:
There I've got one point for acceleration. This is set to slow.
Also there's another option to deactivate the acceleration in games. This one is set to yes.
That works fine for the regular WQ3, because it identifies Quake 3 as a game ----> acceleration is deactivated
But it doesn't work for the SA, because it won't be identified as a game....------> Mouse Acceleration is set to slow!!!!!!
And that's what made me rack my brain...
Sometimes you can't see what's directly in front of you!
Nevertheless I wanna thank you for your help