Hi,
Actully its a typical vmx-300 problem. Actually , It depends on how many channel do you want to preview on the screen ?
VMX-300 allow to show you max 4 channel at one client. It means if you use more then 4 channel on your workspace. You will have a problem .
There is no way to fixed it. We have been using very powerful machine ( i7 ) , Even we want to watch 8 channel on one client . The client gives same error in 2-3 days.
One more thing ; Pelco no longer support the vmx systems