One of the new features in Office 2013 is Hardware Graphics Acceleration which is supposed to improve performance. It doesn't always work well on older computers (and even some new ones). Symptoms include blurred text, cursor hangs randomly, and Outlook freezing for a few seconds (or longer).
I'm seeing a number of complaints where Outlook freezes or hangs and in many of the cases the issue when away when hardware graphics acceleration is disabled.
You can disable the use of hardware graphics acceleration (for the entire suite) from the Options dialog of any Office 2013 application. Each application that is open will need to be closed and restarted after changing the setting.
In Outlook 2013, go to File, Options, Advanced and select Disable Hardware Graphics Acceleration, near the bottom of the dialog.
This value is stored in the registry at
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common\Graphics DWORD: DisableHardwareAcceleration Value: 1 to disable
Administrators can disable hardware graphics acceleration using Group Policy. It's located in the Group Policy Editor under Microsoft Office 2013 > Miscellaneous > Do not use hardware graphics acceleration.
For help troubleshooting general video issues in any version of Office, see
How to troubleshoot video issues in Office programs