In every veriosn of illustrator up to now, Shift+drag is used to constrain an object vertically or horizontally. Why doesn't this work in CS6? How can I get it to work?
Have you tried resetting the preferences already? Start by resetting the preferences the following way: 1) Quit Illustrator if already running. 2) Relaunch Illy by holding down Command + Option + Shift keys until you get a confirmation dialog popup. Choose yes to proceed with launch. For Win, it is Ctrl+Alt+Shift keys.
Some rogues are sometimes mobbing Illy so she gets confused or even downhearted. If you keep them away from her, she may perform better.
You may close down everything else and see whether it helps, then start up other applications and see whether you have a hit.
The usual suspects include:
Some Firefox Add-ons,