Export Audio File Fails


This has happened recently:

After exporting audio files correctly suddenly at 5 or 6 exporting Cubase generates an intense and continuos sound like feedback and the exported audio file appears empty.
After another exporting try it finally produces the correct file and the feedback sound disappears.

WIn 7 64 SP1
Cubase 8.0.5 64
M-Audio Delta 1010LT