Error getting license. license server communication problem: e_adept_document_type_unknown

Question

I began this day with ADE 17.2 and tried every proffered solution to no avail. The last suggestion was to update to ADE 3.0.
The exact error message is:
Unable to download. error getting license. license server communication problem: e_adept_document_type_unknown
I have tried completely disabling the firewall (domain, public, private) and the problem persists. I have tried running ADE as system admin with same results.
I've read all the posts on this forum and it appears no one has found a solution.
Please note: I do not have a proxy, currently all firewalls disabled, no anti-virus software used.
Windows 7 SP 1 32 bit home premium
Firefox 27.0.1
Shockwave flash 12.0.0.70
Network connection is wifi home network
Content to be downloaded is PDF from Google Play Books
Is there anyone who can offer a solution ....
UPDATE:
My husband figured out how to disable the firewall on the router and we tested again (and simultaneiously with software firewall disabled). Still didn't work.
I also created a Firewall Rule specifically for this application:
GENERAL
Name: Adobe Digital Editions 3.0
[x] Enabled
Action: Allow the connection
PROGRAMS AND SERVICES
This program: [local path to]\DigitalEditions.exe
Services: apply to all programs and services
COMPUTERS
[nothing selected]
PROTOCOLS AND PORTS
Protocol type: any
local port: all
remote port: all
ICMP: [default]
SCOPE
local IP: any
remote IP: any
ADVANCED
Profiles: domain, public, private
interface types: [default]
Edge traversal: defer to application
USERS
[defaults]
Authorized: [nothing entered]
Exceptions: [nothing entered]
UPDATE:
I was reading other posts on similar topics and one of the suggestions was to try OverDrive. Since I already have it, I tried it and received the following error message:
The specified OverDrive media file "[local path]\AppData\Local\Temp\Seams-Unlikely-epub-2.acsm" is not valid. (The OverDrive media file root element is not valid.)
According to OverDrive's help forum that means the ACSM file can ONLY be downloaded with ADE!
http://help.overdrive.com/article/0644/What-to-do-if-you-get-an-ACSM-The-OverDrive-media-f ile-root-element-is-not-valid-error-when-using-OverDrive-Media-Console-for-Windows-or-Mac
UPDATE
Have learned we have a WNDR4500 router with built-in firewall which can not be disabled. On the NetGear forums, there was the uninformative suggestion to "use DMZ in the router settings" to disable the firewall. In looking at the settings for our firewall, the nearest screen I could find to resemble that suggestion contained the following:
[ ] Disable Port Scan and DoS Protection
[ ] Default DMZ Server [192.168.1.0]
[ ] Respond to Ping on Internet Port
[x] Disable IGMP Proxying
MTU Size(in bytes) 1500 bytes
NAT Filtering [x] secured [ ] open
[ ] Disable SIP ALG
I'm afraid this is beyond the scope of my understanding and have no idea what I should be doing here so have made no changes.

Answer 1

Adobe Digital Editions Communications Error When Downloading PDF from Overdrive (and maybe elsewhere too):
If you get an “error getting license server communication problem” message in Adobe Digital Editions:
1.  Try downloading any of the PDF files from Adobe here: http://www.adobe.com/products/digital-editions/eBook.html
2.  Now re-download the book from Overdrive
3.  Enjoy!!
I figured this out after many, many hours of frustration . .  hope it helps!!