The error is frustrating but rarely fatal. In 90% of cases, the file is either blocked by antivirus or unregistered due to a Windows update. By re-registering the DLL, restoring from quarantine, or manually replacing the file from your original installation media, you can get your classic CAD software running again.
A rare but possible scenario: Installing a 32-bit add-on or utility that places a 32-bit version of Adlmint.dll into the SysWOW64 folder, while AutoCAD 2010 64 Bit expects its version in System32 or the AutoCAD root folder. Adlmint.dll Autocad 2010 64 Bit