Since i installed the latest release of CSDK (2.7) i have no problem with ADO but i cannot link any Informix table on MDB database because :

RESERVED ERROR (-7711)

There's no message for this error.

Old links (created before the CSDK upgrade) are ok.

Someone knows why?

Reserved error is something Microsoft products say when they don't know what the problem is...
You could:
* try the latest release of CSDK (2.8)
* try and trace what goes wrong. Set the SQLIDEBUG variable on the client side.

SQLIDEBUG=2:c:\temp\infromix_trace.
use sqliprint on the output files to conevert the output from bin to Ascii