Well I'm fortunate that I do not have any other Insteon communications issues with any device. My problem is simply being able to log onto the Admin Console and seeing device status, just like in SunSentry's original post. And like I said, everytime I have the problem, the batch write icons are also not present. Sometimes I need to reload the Admin Console several times before it restores. I've also tried clearing my browsing history and Java cache.
I've now also verified that disabling AV and the firewall has had no effect. I haven't been able to try https yet, but will happily post the results from that as I would love to find a solution to this.
Thanks to all who are helping to find a solution.