Using Verions I of the API why can't I pull Custom Modules?

Using Verions I of the API why can't I pull Custom Modules?

I have some .NET code that calls the version I web services 
using the  https://crm.zoho.com/crm/private/xml/LinkingModule1/getRecords

If I do a standard module like Contracts it works. But not for The above custom linking module. 
LinkingModule1 shows in the list of modules but I cannot pull the data. 
From what I understand the client has Enterprise Edition. 
What am I missing? 
and thanks ahead