You may occasionally receive a drawing from an outside source that causes this problem. Simply type VIEWRES at the command prompt, say YES to fast zooms, and set your circle zoom percent to around 200.
Why does the Object Properties Toolbar Stop Working?
When you pick objects at the command prompt, they highlight and grips appear. On the object properties toolbar the layer and/or color of the object usually appear so that you can change them. But on some systems this stops working. This is because the noun/verb selection has been turned off. Simply type DDSELECT at the command prompt and turn on the 'Noun/Verb Selection' toggle. The Object properties toolbar will start working again.
Number of Command Lines
When you press F2 and look back at the command history, you may notice that at some point it stops. The default number of lines is set to 400. On R14 you could change it in the preferences dialog. Unfortunately 2000 and higher has regressed. You have to use a to lisp expression setting like MaxHatch.
To check the current number of lines set:
Command: (getenv "CmdHistLines")
To set a new maximum number of lines:
Command: (setenv "CmdHistLines" "1000")
The number you use must be in a range from 25 to 2048!
Lost Command Line
Almost all AutoCAD users utilize the command line area to some extent. Recent versions of AutoCAD allow it to be turned off and it can be as easy as accidentally pressing Ctrl + 9. You can use these commands to control it.
Keeping the UCSICON in the corner
If you don't use a UCS you might as well use UCSICON off. If you do you might want to keep it in the lower left corner. Use the 'Origin' and 'No Origin' options of the UCSICON command to control the position of the UCSICON.