redirect uses mod_alias is it turned on ?
see
http://httpd.apache.org/docs/1.3/mod/mod_alias.html
I am also pretty sure it will ignore the the params that are supplied hence it will simply pass the input argument to the output which is presumably what you are seeing as both sides are index.php
I think you need to use rewrite rather redirect but I dont have access to my systems at the moment to create a test rule
tkgafs