Unable to upgrade my ZD1100

[support_eona]

Hi!
I have a ZD1100 with  firmware 9.6.1.0.15 and Two AP zf7372.
Today, it's really hard to connect the Administration because updated web browser block website using RC4. So I have decided upgrade my ZD.
I saw that it wasn't possible to upgrade directly to 9.10.x, so I have started with firmware 9.8.3.0.44.
I get the page "Upgrading 0%" then... nothing. After 1 hour nothing changed, so I have restarted ZD box.
When restarted, I can access to my administration interface, I'm still in 9.6.1.0.15, but my two access point can't contact the ZD (I have message "Model[zf7372] is not supported"). But acording this ticket (and because it was working before the upgrade), it should be supported!
Anyway, I have tried to upgrade my ZD with firmware 9.8.1.0.101, 9.6.1.0.15, I have always the same problem.
Pluggin a console cable, here is the output when starting an upgrade:

grep: /etc/airespider/authsvr-list.xml: No such file or directory
tar used greatest stack depth: 12552 bytes left
lwapp_release: proto=2, refcnt=2
lwapp_sock_destruct: refcnt=0
lwapp_release: done proto=2, refcnt=0
lwapp_release: proto=1, refcnt=2
lwapp_sock_destruct: refcnt=0
lwapp_release: done proto=1, refcnt=0
br0: port 3(vif0) entering disabled state (ifconfig,1974)
device vif0 left promiscuous mode
br0: port 3(vif0) entering disabled state (brctl,1975)
br0: port 4(uif0) entering disabled state (ifconfig,1976)
device uif0 left promiscuous mode
br0: port 4(uif0) entering disabled state (brctl,1977)
NET: Unregistered protocol family 30
Exiting
Stop netlink server

So, here are my question:
- Did I do something wrong?
- What can block the ZD upgrade?
- What can I do to establish the connection between my AP and my ZD?

Thanks for your help!

[roy_jorolan]

Thank you for this. 

[support_eona]

You are probably right, I was using IE 9 because my chrome and Firefox were up to date, so not working on the old version.

[jeff_bingham]

 I recently had this issue and Support had me download Firefox 45 and then surf to about:config, search for and change security.tls.unrestricted_rc4_fallback to user mode. I just clicked on it once to change it and then I saved the settings and performed the upgrade and it actually worked slowly but surely. I went directly from 9.6.1 to 9.8.3.0.44