Hi,
Realistically making sure your router is also set to the same Time Zone as the OS is just as as important.
In most cases it is a questions of checking which settings have changed on installing Lion compared to a Snow Leopard set up.
As you say it could be as simple as the Date and Time Setting
Just as easily it could be the current settings for Face Time in the Firewall.
Or the Language settings
More likely the DNS settings in System Preferences > Network.
Possibly the Ownership and Permissions of the Home Folder, it's Library or individual Preferences .plists
Turning Off Face Time in it's preferences and Quitting, then restarting and turning it On again will let you know if you can Write to the .plist
(Quitting IMAgent in the Activity Monitor and then restarting Face time certainly will Write to the .plist)
Checking the My Card (Head and Shoulders icon) in the Address Book would be another check to do.
In fact anything that has occurred at other Upgrades (Panther to Tiger, Tiger to Leopard etc) would be wise.
At present I am following several Face Time threads but cannot "see" a common "Fix" to any of them.
The number of people involved suggests that a "common" fix is more likely.
Nothing is clear at the moment and "this worked for me" statement would be the way to go.
10:03 PM Thursday; August 18, 2011
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb( 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously