This error occurs in a Microsoft Access database that seems to work fine on every other machine but one. The MS Access database actually loads and runs, so the code is compiled and functional. Then it dies on some very common code such as CurrentProject.Connection for ADO to open a table or query recordset:

Confusion

The “Class Not Registered” is very confusing. It implies code that won’t compile or broken library references but that’s not the true cause. Is the Access database corrupt? No.

We’ve received reports for this error for years and were never able to reproduce it. We finally did and figured out why it occurs and how to fix it. Read our new paper Microsoft Access “Class Not Registered” Run-time Error ‘-2147221164 (80040154) to learn more.