I have upgraded our BorderManager servers at our principal site to 3.9sp1.
I'm really happy with the iManager integration and have even attempted and succeeded in setting up C2S VPN access with only an hour or so immersed in Craig's manual... so overall very happy with it...
..but... and there's always one of them loitering in the background... I have found staff no longer can use a specific secure site they use to place business since the upgrade.

Once logged in to the site they can browse about, input data but as soon as they try to accept, update or try any of the (what seems to be javascript) buttons used for in-site calculations or searches, the whole thing hangs....

They are able to access the site fully from an non-upgraded NBM3.7 server at the DR site, which is nice for the moment, but isn't a long term fix.

I have looked at the working server's filters, access control lists and proxy.cfg files for anything obvious (and it would need to be very obvious) but to no avail... filters are very basic on the working machine, mainly just allowing http and https proxy entries...

The proxy.cfg file on the working server was Craig Jonson's version 21 and the new one version 30... I have tried running with the additional entries (to v21) remarked out but the problem persists...

Could anyone suggest a way I can trouble-shoot this...?

It might be useful to know that the site is one of those IE friendly sites and would, before chatting to the "it's your firewall" support team, re-direct you to the secure login site by displaying the site URL in a Firefox display window...