Hello again,
to cut a long story short I have determined that the fault lies with the 8800. In essence I turned off all encryption algorithms except for the rsa_des_ede3_sha and found that I could access the EDMs on 4xxx and 5xxx equipment, and could also https: to other internet sites and internal servers just fine … the only fail was the https: to my 8800s EDM.
Paul L … if you get a chance would you mind cranking up Firefox v27 and trying to access one of your 8800's running 7.2.11? If it works I'll just drop this whole thing, if it fails I will log it with Avaya.
Observations:
88xx has 5 algorithms to choose from, the rsa_des_ede3_sha is it's FIRST choice when accessed by Firefox and it breaks.
4xxx and 5xxx have 5 algorithms to choose from, the rsa_des_ede3_sha is the LAST choice when accessed by Firefox and still works anyway.
I don't seem to be able to revert to Firefox 26 to see if this algorithm exists and if so, whether it gets selected (and works).
The list (in preference order) for Chrome, shown here -
https://code.google.com/p/chromium/issues/detail?id=58833 , puts this algorithm at the bottom so I am surprised that the 88xx selects it first over other stronger candidates.
Cheers