RSView server client problem

We have a RSView SCADA set up with an active display server running five RSView active display floatin clients.
When the alarm log activates and the audible alarms on the server PC sounds the acknowledge button on the server display does not silence the alarm, all the client display acknowledge buttons silence the alarm??
To rectify this problem we shut the server display system down and restart.
Anyone out there had any similar problem?? and do you have a different fix??

Thanks Mike