When configuring Quickbooks 2012 for multi-users an error can occur from the client stating that you need to change your firewall settings even if your firewall is turned off. This message may also relate to a file permissions problem. Intuit recommends that the user group everyone have full control over the share permissions and the following user accounts have full control under the security tab of the folder:
Administrators
Creator Owner
Everyone
QBDataServiceUser22
Users
The problem still persisted and it was discovered that whenever the host computer opened the company file it was no longer accessible by any client computers. This problem was caused by the host computer having dual network adapters and QuickBooks would bind to the wrong network adapter and therefore have the wrong IP address and be on the wrong network. This was resolved by changing which network adapter would be bound first.