AutoCAD gives AcDs Error: Signature Mismatch on the Command Line

January 26, 2022 Jeff Lotan


When you launch AutoCAD Civil 3D 2020 you receive “AcDs Error: signature mismatch” on the command line and it takes a long time to fully open.





Command: AcDs Error: signature mismatch


Command: AcDs Error: signature mismatch

AcDs Error: signature mismatch


It was taking about 10 minutes to open Civil 3D 2020 (not double clicking the drawing).

We saw it was throwing an error with the BlocksPalette (see above).


This problem was caused by a bad / corrupt block that was on the Block Palettes “recent” list in AutoCAD Civil 3D 2020.


We closed the block palette and saved the workspace... closed/opened C3D and it was much faster.

We loaded the palette again and it was slower.

What resolved the problem was to right click on each block in the Blocks Palettes “recent” list and remove them. 

You could also remove several blocks and test.

It may have only been 1 or 2 blocks.  Watch which blocks get inserted going forward and if things get really slow again, then removed the last few blocks and run recover/audit and purge on them.

About the Author

Jeff Lotan

Sr. Technical Support Specialist - Licensing<br><br>I am charged with mentoring and training team members in the proper use our systems and tools, documenting NSC processes, and providing feedback and ideas to the management team towards improving the customer experience. I am also a major contributor to our technical support blog and internal knowledge base.

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