One of the things that I love about AutoCAD is that most fixes can be easily identified and completed rather quickly. I recently had a client reach out to me concerning some functionality that was no longer working as expected in their AutoCAD 2010 product. Both of their issues stemmed around a system variable that had been mysteriously changed.
The first problem my client had was a missing Quick Properties palette. She loved the ability to select an item in AutoCAD, and to use the Quick Properties palette to quickly change the layer, color, linetype (among others).
The solution was to type in QUICKPROPERTIES at the command prompt, and to enable it by changing it to 1. There are options available within Quick Properties to allow greater functionality that have been developed since 2010, so if you like Quick Properties, be sure to check out Help in AutoCAD to learn all about it.
The second problem was that she lost the ability to double-click on her MText in order to edit the text. We checked the DBLCLKEDIT system variable, which was set correctly to 1, then we proceeded to the Options dialog. The Noun/Verb selection checkbox was not checked. I had her select it and click OK to save the change and exit the Options dialog. She was now able to double-click on her text to open the MText editor.
The moral of the story is that it's pretty easy to get things working again when they've gone awry. Usually, a quick search in the AutoCAD Help system can help you find the solution.