Hi,
"Just to restrict the set of possible influences: What happens when you
start VE Pro / MIR Pro as a stand-alone application on this system? Same
situation?"
I did not have the issue in standalone just now...I hate to complicate things but :) it doesn't happen all the time. It happened the first time when opening a older project. This time MIR was working great but when I merged current project (had flute-piano-vibes etc) with a trumpet/sax patch I got the problem you are seeing. I am sorry to admit that issue is intermitant lol
Do you need any info from system which may help you?