In short, Kaseya RC does not co-exist with a standard WinVNC installation.
Your options are to either use a different VNC product for direct access to the machine (e.g. Ultra VNC, Tight VNC) or to use a different RC type with Kaseya (e.g. Terminal Services or Radmin).
If the non-Kaseya VNC installation must be utilized, then use RDP/Terminal Services as the Kaseya Remote Control method.