Agent type is inappropriate

I have developped an Agent/Lotus Script, executed via the C++ Notes API. It works fine on the Test Domino Server (version 8), so we copied this agent to the Production Server (v7).

When we execute the agent on the Production Server, we have the following error :

“The agent type is inappropriate” (error INVALID_AGENT_TYPE in the C++ API)

I had a look at the documentation and Google, but I found nothing about this error or how to solve it. Dit anyone ever experienced that ?