In AutoCAD Mechanical, there is a dimensional feature that can add ISO fit tolerances such as H7 or f6 and such. A user lost his list if fits and wanted to get them back. The problem was that his Mechanical VAL tables were lost (how, I do not know). To fix them, we copied a set from a working computer to "C:\Users\Public\Documents\AutoCAD Mechanical 2012\ACADM\GEN". We copied the VAL folder and all of its subfolders to get them restored.
This one doesn't come up too often, but when it does it is slightly hard to find. If you need to make a resizing box around your text in AutoCAD, try the TCIRCLE command. Just type in TCIRCLE and select the text you need to "box in", enter your preferences, and wala "boxed in text".
A user had his Viewport Layer change upon creation of the viewport from modelspace to paperspace. He created it in modelspace on layer AM_VIEWS and when creating the viewport in Layout Space, it would switch to the current layer. The solution was to go into OPTIONS >> AM_STANDARDS and check the state of the checkbox "Apply new settings to layers...". This setting can get out of sync at times.
A user here began having strange behavior issues in his AutoCAD sessions. His explode and purge programs would not open as command line entries (even when he typed in "_PURGE", etc..). His LISP routines would pop up dialog boxes even when the variables were to set to keep them closed. Through a lot of diligence on his part, he found that the variable QAFLAGS might be the culprit. He looked at his setting and it was set to 17. All other users here were set to 16. He set it to 16 and tada, his AutoCAD is back to normal. A great find on his part. I hope this might help others.