I've searched but didn't find anything exactly like my issue.
I have a Dell system running Windows 7 x64 and have 2 identical Acer V226HQL monitors.
When physically at the machine, I see both displays fine. Windows display properties shows the monitors as 2 and 1.
The ATI Catalyst panel shows both monitors but as 1 and 2.
When I remote in using TeamViewer, I only see 1 of the monitors. I have to go into Windows display properties and use Detect. At that point, I'm shown a smaller physical display and when I attempt to use Extend Desktop, I get a pop-up with the title 'Change Settings' and a message saying "Unable to save display settings"
This used to work using TeamViewer and I don't know why it's not now. I've tried back-leveling to an older version, but no dice. I'm now running the latest version again.