VST volumes drop to 1/3 for no reason.

When I am recording a part on a vst, any vst, the volume will drop very low at random times and I have to completely reload the vst in order to get it back to normal. It is not the actual volume “knob” within the vst. According to the vst, the volume is the same. However within Cubase the volume is around a third of what it should be. I can’t think of anything that could be triggering it because it always happens at completely random times when I am playing a part. I have tried filtering different parts of the midi messages, thinking it could be a stray midi message triggering the bug, but so far nothing has worked.

best,
Jim

Cubase 7.0.7
HP p6813w
AMD Athelon II x4 645 Processor 3.10 GHz
6 GB RAM
64bit Windows Home Premium

Are the VSTi instrument tracks? Or in the rack?
Can you take a screenshot showing the VSTi, the MIDI Track, and the Mixer output tasks at a time this is happening?

couple of possibilities… make sure the windows audio auto gain control is off… check that cubase power scheme is on
dont know if that would have any effect but worth a try