Reason for Invalid Decomposition Command in CAD
If you are unable to explode a block in CAD, try first to explode other entities such as multiline text or hatch patterns. If those entities can be exploded, it means the selected entity itself cannot be exploded. However, if none of the entities can be exploded, your CAD system might be infected with a virus program named acad.lsp, which is based on the AutoLISP language.
This virus causes the ‘explode’ command to become invalid whenever you open any drawing, severely disrupting your workflow. When active, the virus creates the acad.lsp file in every directory where CAD drawings have been opened, and it also generates the acadapp.lsp virus file inside the CAD installation directory under the Support folder.
How to Remove the Virus:
- Open the Windows system search dialog by choosing “Search for files or folders.”
- In the “File or folder name” field, enter:
acad*.lsp - In the “Include Text” field, type:
explain - Set the “Look in” option to search all hard drives.
- Delete all files found through this search. Removing these files resolves the problem.
Important: Be sure to search through all directories on your hard drive to completely remove the virus.
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