The filter is probably a corner or box filter.
As for the 404.. my 405 leaked a little as well. I tried everything, and the ONLY thing that would work was vasoline. Obviously, it's probably not the safest thing in the world, but it works great. I wouldn't suggest getting it on anything inside the can, but just a little coat on it did it for me.
"What, exactly, is the internet? Basically it is a global network exchanging digitized data in such a way that any computer, anywhere, that is equipped with a device called a 'modem', can make a noise like a duck choking on a kazoo." - Dave Barry