Outlook, AD or DNS issue?

Trying to move away from the &%$#$-ing 2008 SBS & yet another issue rears its ugly head.
When trying to run some of the pending updates, true to form, it rebooted & never did get to the desktop. I restored from a backup, but since then, network shares weren't available. They showed up with the red X on them & when double clicking, I'm getting the message;
\\Server is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions.
Logon failure:The target account name is incorrect.
Permissions haven't changed & name is correct, as has been the case since it was installed.  
I can ping the server by name or IP without problems.
If I go to map network drive, as soon as I select the server, I get that same message. But, if I put \\\share it maps the drive, no problem. Now, since I'm in the process of replacing this, I just re-created the shares on one of my new & improved servers, remapped everyone to those & all is well & I am only including all this, as it may lead to a solution my to bigger problem.
My bigger problem is when someone is using the remote desktop server (2008 R2) & tries to open outlook, a dialog box pops up,
Connecting to mailserver.mydomain.local, along with username (domainname\username) & a password box.
Entering password doesn't work, so Outlook never opens.
A few other things to consider as a possibility here, that version of outlook is 2003 (yes, I know - when new servers are up & running, office version will be 2016), so I'm wondering if any server updates, could have 'broken' this?
FWIW, email can still be accessed via OWA on this (or any) computer. Also, no users in office having any issues with Outlook, but they are all running 2007 - 2013 version.
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Shaun VermaakTechnical SpecialistCommented:
How old is the backup?
gromackAuthor Commented:
Maybe 2 days?
gromackAuthor Commented:
I found a fix for it - in the security settings of Outlook, it was set at Kerberos Password Authentication & I changed it to Password Authentication (NTLM).
Don't know how that would have changed & figure I didn't have the same problem elsewhere, since all the other clients are using 2010 or 2013 & the ones I checked were set at Negotiate Authentication.
How could this have changed, though?
Shaun VermaakTechnical SpecialistCommented:
I do not think it changed in Outlook. I believe Kerberos authentication stopped working. Is time correct on all sides?

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gromackAuthor Commented:
I think you're right, as think I saw something in the event viewer about, but am wondering why it would stop working?
I have been currently trying to get all updates, so I can migrate away from this & drop it off of the nearest, tallest building, but am currently waiting on a restore from backup, as it just doesn't want to work with me!
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