Have you tried combinations of the FQDN of your AD domain
Have there been any AD upgrades/new trusts/new domain controller done recently that coincides with the time it started to fail?
Is the username that your using valid, has it had it's permissions changed recently?
The solution to the KB entry you quoted suggests that the issue is with Active Directory and the username used and not EPO.
Yes have tried all combinations....i can see in the event log on the DC a success audit for the connection of the account that i am using. The orion log also gives me this error: "unable to associate user with task", and then " unable to find user in the domain"
The username and password are valid and the connection test succeeds.
Is the AD user a global administrator within EPO?
EPO 4.5 Build 753 is the RTW version, current version is Patch 4 + Hotfix 1.
It may sound trite, but please consider patching your ePO server to current levels as there's been quite a few Ldap fixes incorpoprate in the subsequent patches since release.