If my advance search results are on multiple pages (more than 50 items), when I click on another page, the advance filtering goes away and it brings back ALL search results.
For instance, advance search "magazine" for PS1 [NA] and you get 51 results across two pages.  When I click page 2, it returns all 257 results across 6 pages.  The url loses it's &platform filter.  I can manually add it back to the url to get the proper page.  Hope this helps!  
BTW Thanks for your help Matt.