404 error with only one GET variable

[eluser]jaystang[/eluser]
Hey Guys,
I'm new to codeigniter and I'm hoping some of you can shed some light on how some of this URL stuff is suppose to work.

I'm working to develop a heavily dynamic ecomm site using CI. For SEO reasons I love how CI structures the URL like a directory, however once I get deep into browsing a specific category (think of amazon.com when you're drilling down via the left nav to filter out products) I am forced to use GET variables based on the users selection. Since there is no telling what the user is going to filter by next I can't assume a certain position in the URL for a certain variable. So with that said this is what I'm trying to get my URL's to look like.

http://domain.com/products/browse/produc...=something

So for my code I have a "products" controller with a "browse" method in it that takes in two params, "producttype" and "productcategory". Now with that said I feel like I should be able to access "filter1" from my "browse" method. Instead I get a 404 error. Now the real interesting part is if I add one more GET variable on my url it all works. For example...

http://domain.com/products/browse/produc...mmyvar;You see I have the same URL as before only I added a dummy GET variable on to the end. My code properly picks up the $_GET['filter1'] and I no longer get a 404. Obviously I don't want to have a random dummy variable on the end of all my URL's for no reason. Also it doesn't matter the position of that dummy var. If you switch filter1 and dummyvar it will still work.

Currently my config has the following...
$config['enable_query_strings'] = TRUE;
$config['uri_protocol'] = "AUTO";