If its indeed a class not registered error like Thomas Pointed out, try running this command in a command prompt running as administrator
regsvr32 "path to your dll"
Other SO question for reference
I should also point out that this error could also mean that the name of the dll you specified in the registry key for EA might not be the same as the name of the registered DLL.
Some precisions:
Adding the key only tells EA what to look for in the Registered dlls library, but you still need to register it to the dll library.
If you are debugging with visual studio, there is an option for making it register to the com library when you start debugging