Stefan,
You cannot use Informix CSDK 64bits with Genero GEP 32bits, you need to install Informix CSDK 32bits.
I believe that you have got SQLite library in 32bits, this is why you can use the SQLite driver.
You better install the Informix CSDK 32bit in a different directory as the 64bits Informix server and CSDK, and make INFORMIXDIR point to that directory.
Best regards,
Florencia