Mac Retina has got a superb display, but it seems that not everything is compatible with that excellent resolution. The cause appears to be the switch between the two graphics cards included in the device.

Sametime client has some known issues: MAC 10.8 Retina ST AV - Known Issues.

In January a fix for Sametime 8.5.2 was published for Mac Retina and Windows 8, but not all the problems have dissappeared, though many of them have workarounds:

• Mac 10.8 Retina : Blank video window when starting an A/V meeting
• Mac 10.8 Retina - Video Camera Preview does not display in Voice and Video Preferences when accessed for the first time after launching Notes
• Intermittent call failures using Sametime Unified Telephony and calling from Windows 8 to Mac Retina
• Mac Retina : Call initiator's video does not display in a point-to-point call
• Mac Retina : The last user to join an A/V call cannot see his local video and when the call switches to that user, everyone sees a blank image
• Mac Retina : Call initiator's video does not display in a point-to-point call