Black Lion Trading
Work with support. They have had good success helping others with similar issues.
Often, making sure that you launch GW2.exe with admin privileges prevents this from happening. If you’re on a Mac, today’s update was supposed to address a similar problem.
Finally, there’s a small chance that your anti-malware software is preventing awesomium.exe from running — that’s the app the game uses to access to the TP (it’s sort of 3rd party browser designed to work within games). See http://wiki.guildwars2.com/wiki/Trading_post#Trivia for a link to the company’s website.
John Smith: “you should kill monsters, because killing monsters is awesome.”