Error when getting over 20 results

I have the following ZSQL method:

select * from pmember where project=<dtml-sqlvar project type="string">

The result should be about 60 records. However it only works if I set 
"Maximum rows to retrieve" in the "advanced" tab to a number below 20. 
If I don't, I get the following error:


*****************
KeyError
Sorry, a site error occurred.

Traceback (innermost last):

     * Module ZPublisher.Publish, line 175, in publish_module_standard
     * Module Products.PlacelessTranslationService.PatchStringIO, line 
51, in new_publish
     * Module ZPublisher.Publish, line 132, in publish
     * Module Zope.App.startup, line 204, in zpublisher_exception_hook
     * Module ZPublisher.Publish, line 101, in publish
     * Module ZPublisher.mapply, line 88, in mapply
     * Module ZPublisher.Publish, line 39, in call_object
     * Module Shared.DC.ZRDB.DA, line 337, in manage_test
     * Module DocumentTemplate.DT_String, line 474, in __call__
     * Module DocumentTemplate.DT_In, line 602, in renderwb
     * Module DocumentTemplate.DT_Var, line 219, in render

KeyError: 'query' (Also, an error occurred while attempting to render 
the standard error message.)
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Any idea what the problem is ? I'm using ZMySQLDA 2.0.8 and Zope 2.7.5 .