changing class expressions on-the-fly

[David McGaughey]

Greetings!

I'm very new to mapserver, so please pardon this newbie:

I'm trying to modify expressions on the fly.  I build my URL the
way that I think it should go:

http://clic.ci.lubbock.tx.us/cgi-bin/mapserv?map=/home/httpd/clic/gis/pntest.map&map_layer_1_class_expression=173953&name=pn085

But my server tells me:  Internal Server Error

I'm running Apache 1.3.9 and mapserv 3.3.7

Can anyone help? 

Greatly appreciated!

David McGaughey
City of Lubbock, Texas