Becomes non-responsive using certain combo of filters

If I select a combo of filters from the categories or tags where there ends up being no product fitting the criteria; the page becomes non-responsive after I uncheck one of the options or try to hit clear. I have to reload or go back. Why is this and how can I fix it?

For example on my site – if you select a BRAND and then a PRODUCT that that brand doesn’t have, it will end up freezing and needing to be reloaded. I want to be able to allow customers to select a brand and then a type of product carried by that brand. It works great when a product fits the criteria but gives this issue when there is no result.

The page I need help with: [log in to see the link]