Hi Mel,
Basically, what the error says is that the program is unable to instantiate the SAPbobsCOM.Company object due to a difference incompiling mode between your application and the DI-API.
Just in case, to complete $riniva$ answer: SBO version has to be the same as the addon.
So, do you confirm th have installed the 32bits client? If yes, then and only then, your application should be compiled as x86.
Regards,
Eric