It may not be what it seems in this case.
Some time ago, we instituted a change to the pawn shops whereby the ones that were in typical "low-level" areas, primarily those which were considered starting areas (or nearby to starting areas) would not have a conversation with anyone over a certain level. This was done because of the description you gave above...that people would make a mad dash rush to the pawn shops in places like Port Hempstead, cash in all their high-value loot and rapidly deplete the shops. The problem with this behavior was that it really hurt the players of low-level characters, who did not have the ability (and in some cases, the knowledge/experience) to travel to places that were farther away to use the pawn shops. As Charm said, it's not exactly an issue with the pawn shops but rather very much a player behavior.
Getting back to this specific instance, I would actually be really surprised, given our current server population and the day/time in which I reset the server, that the Port Hempstead pawn shop was depleted, though it naturally is possible. My guess is it refused to talk to you because of your character's level. It would be worthwhile to try a few of the more far-flung pawn shops, some of which are easily accessed via portal and/or ship.
