Dave Smith Instruments SYNTHESIZERS

Today I noticed a weird problem with my Evolver. There's a constant noise in
the rythm of the amp envelope that stays even if I turn all oscillators off:
http://www.trippler.net/files/mp3/evoprob.mp3
The mp3 starts with ringmodulator and a sync osc, which both are turned
down.
The noise sounds like a saw osc playing with constant pitch, it is not
tunable regardless which osc pitch I change, is not influenced by the master
tune value, doesn't react on midi note number though the oscillators do, and
gets louder if I increase the VCA level (audible near the end of the demo
mp3).
I am sure that there is no modulation in the program that can cause this, it
happens even in an initialized patch.

Someone knows what's wrong here ?

Regards
Stefan