Hi,
Go to IIS server
1) Right click on Symantec Webserver --> Properties --> Home Directory --> Under Home directory there is an option Execute permissions : change it to Scripts and executables.
2) As you are using windows XP, don't keep all the clients under same group.
Create new groups if not present, move clients to different different groups.
3) Change hear beat interval to 15 minutes, & keep 5 minutes difference in heartbeat interval for every group.
eg. Group A heartbeat interval 15 minutes, Group B heartbeat interval 20 minutes so on.