Slow AutoCAD startup or performance

Here are some tips that might help.

Generally with antivirus software's try to disable them if you find that AutoCAD performance is slow typically during start as well as opening and saving of files. If it seems like it is the antivirus software that is the cause try to make exceptions for for example the install folders of AutoCAD, specific file types like DWG,AC$, SV$. Set to scan for write operations only for acad.exe should be safe.

If changing annotation scale in a viewport takes long time try resetting the scale list in  the drawing and its xrefs. Make sure to reset the scale from the bottom of the xref tree, one drawing at a time and last in the host drawing.

Knowledge Base documents worth looking at:

• Program slow to start when Microsoft® OneCare™ anti-virus software is enabled
• AutoCAD® freezes during startup
• Improve software performance
• Possible causes of slow drawing performance
• AutoLISP® and other types of routines run slowly
• Performance impact when toolbar transparency on
• Errors or performance problems when working with objects in large coordinate space
• Drawing takes long time to finish loading - when drawing contains a lot of 3D solids
• Performance problem when exploding multiple polylines
• Loading XREF drawings and inserting external blocks is slow
• Copying and pasting objects - When copying and pasting objects, you noticed that it takes a long time for the operation to finish.

Outside The Box also has a tip to disable the AutoCAD InfoCenter. It's related to seeing these dialog boxes and started after applying SP1.

Microsoft Visual C++ Runtime Library
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Runtime Error!
Program: C:...
R6025
- pure virtual function call

Followed by this message.

Microsoft Windows
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Autodesk Communication Center has stopped working
A problem caused the program to stop working correctly. Windows will close the program and notify you if a solution is available.