I was getting this error constantly today, so I went to Settings>Applications>All>Voice CommandSettings
→ Applications
→ All
→ Voice Command
. From there I clicked Force Stop, OKForce Stop
→ OK
then Clear Data, OKClear Data
→ OK
. Then I relaunched the voice command by tapping the microphone button on my Google search widget.
The Voice Command worked perfectly, and I haven't seen the error message in about an hour.
I hope this helps.