Unless you where switching hardware it might have been best to upgrade in place that way the ini/stconfig.nsf would have been updated.
See what the diffrences between the old sametime.ini and the one created by the new install. Make sure anythink you added to the old ini is added to the new ini
Do the same with the stconfig. Copying a old file back over between versions is not recommended
I take it this is the same physical server?
Also there is a ini that will allow concurrent logins even though I think that is a bogus error message