I just add a new VGA to a rig, now it has 5 vga.
When i try to start mining i have this problem:

X Error of failed request:  BadValue (integer parameter out of range for operation)
  Major opcode of failed request:  141 (ATIFGLEXTENSION)
  Minor opcode of failed request:  67 ()
  Value in failed request:  0x17
  Serial number of failed request:  18
  Current serial number in output stream:  18

dont know why....