Hi Len,
The fact that the F5 key refreshes the values of the mimic indicates that the Modbus link and gateway are running properly. I have just downloaded Firefox 3.6.13 and I checked one of the gallery mimics in live mode:
http://www.whzan.com/viewer.aspx?MimicID=578#
Then have a look at the sub screens, some data should be changing.
It works ok, please could you check the mimic as well? If it works then there is some issue with your own mimic (which we will investigate) if it doesen't then its with FF 3.6.8 (could you update?).
I have sent you a direct email via your registration email address, if you want one of our developers will work with you to clear this issue.
Thanks Keith