it could be the result of the following.
how many screens with pushbuttons that are set to .25 seconds or faster? the more pushbuttons, switches, and other items that have short times mean the panelview communications are more crowded.
how many plc's are connected to the panelview.
how many nodes are being used? maybe not the right term here.
how much memory is left?
how many applications are loaded?
hope this helps,
james