Hello again Mac,
I just re-installed RB 2010 over my current installation and started the Setup with Administrator credentials. Afterwards I also reinstalled the 2010.5 Build 2 upgrade for RB.
But unfortunately the problems still occurs

I can play an existing tune but when i press the option [Midi Drv] and then just close that dialog by pressing Cancel RB terminates.
By the way, the UA-700 is an external (ASIO) soundcard connected to the PC with USB, so not an internal PCI-card in a PC slot.
Greetings, Valentino