asterisk users - Mar 2007 - Testing asterisk with sipp

Hi all,

I'm trying to use SIPP (http://sipp.sourceforge.net/) to stress-test our 
asterisk installation. We have a very simple dialplan that uses FastAgi. 
I'm finding that all calls to "GET VARIABLE" from the FastAgi are 
returning null when the dialplan is invoked from sipp -- and they work 
fine when invoked from a softphone on the same machine, for example.

Does anyone have any insight as to what might be going on here?

Thanks
John