Hi There,
You may want to have a look at
http://www.openlinksw.com
you can download a fully functional eval driver from here.
The error you have looks simlar to either environment problems or a permission problem
it might be worth checking the Informix Required settings over to ensure all are correct, if a windows based server, then run setnet32 to do this.
sometime setting CLIENT_LOCALE=en_US.819 can resolve the problem?
Personally I work with the OpenLink Drivers regularly and connecting to Informix Database either locally or on a remote machine has proven to be quite an easy process in the past, so you should not experience too many problems.
HTH
BR
John