In my custom objects, whenever I click on a list item from the Custom Object Tab, on the main page layout there is always a "Back to List: Custom Object Definitions" link in the top left of the page, instead of going back to the main Custom Object Tab.  Does anybody know what's causing this or how to fix it?

I have a custom object in our Salesforce setup called AgentProducts, when I do a query (code running in php) via the API the only field I can get back is Id;

select Id, User_Id__c from AgentProducts__c

returns a record for every one of the entries in AgentProducts, but only with the Id field;

Array
(
    [0] => stdClass Object
        (
            [Id] => a0350000008xWWKAA2
        )

    [1] => stdClass Object
        (
            [Id] => a0350000008xWWLAA2
        )
etc. 

Even worse, if I filter the query by something like my custom email field, I get back the correct Id for the correct account, but still, no further data;

select Id, User_Id__c from AgentProducts__c where Email__c='xxx@xxxxx.xxx'

returns:

stdClass Object
(
    [Id] => a0350000008xWWMAA2
)

Any ideas?  I've been looking through the online documentation but I can't find anything on custom objects needing special treatment.