Error on page

Hi,
I have just installed Desktop Manager 6 Professional Edition with 100 licenses- single user and have noticed that when I try to view a report e.g. Computers by Age and change the drop down from 25 to 100 I receive an error and nothing happens. This is the error I am receiving:
Line 19
Char: 1
Error: 'null" is null or not an object
Code:0
URL: http//itmonitor:8020/inventoryReports.do?
actionToCall=showHardwareReports&invCategory=108&selectedTreeElem=1113&reportCategory=200

I am using IE7 with all of the latest updates and have added the Desktop Manager URL to my trusted sites.

This appears to be happening not just in this report but in all of the inventory reports. If I choose User Logon Reports to see who is currently logged in I do not even get the 25-100 drop down option. Has anyone else experienced this?
Any suggestions?

Thanks,
Nickl