strange intra-website surfing timeouts

I work in a suite of Executive Offices occupying two floors of a downtown highrise.  Each office/business has data jacks routed to a wiring closet whereby the occupant can tap into a shared internet connection. The connection is a dual T1 setup and bandwidth is plentiful.  We are able to maintain separate external IP addresses (static) which are doled out, if i am not mistaken, by a managed switch.  There are a stack of Linksys/Cisco/Dlink routers in the closet for each company occupying a suite(s).

About a month ago, we started experiencing a strange problem when using the internet which causes any number of sites to 'stall out'.  in other words, i can be within a particular website, click a link, click another link, click another etc....everything is working great....BUT....on a completely random basis, a given page within a site will just stop responding.  it's VERY typical for it to happen if using a site's Search function. Typically the browser will time out before the page comes up...and in best case scenarios, it takes a minute or two for a page to come up, at which point, ironically, everything begins working quite well again.

I am convinced that the building management has misconfigured something or has a failing piece of equipment in the wiring closet, but i'm wondering if these symptoms don't ring a bell with someone....MTA mis-setting?  cache timeout of some sort?  limit on concurrent connections per IP address?  any thoughts or ideas for diagnosing are appreciated.