Take a look at this forum thread:
http://www.perceptiveautomation.com/php ... light=acgi
Not sure if this is the problem you are seeing or not. Are you using the ACGI Dispatcher 2.0 beta? If so, you might want to try the non-beta version. The version I have posted of the Indigo script I got working with the beta though, so if you recently downloaded the Indigo CGI script then I would think it should work regardless of which Dispatcher version you are using...