I can diagnose where a search for the problem should begin, but not so much the specifics. My guess is the issue is in the plug-in.
WordPress is designed to read constantly from a database and it's reading something that looks like %TITLE%. Now I've never experimented with QTranslate, but my assumption is they are adding additional database entries for the various languages and then each post, in their respective language, is supposed to pull from it's own database.
It could be something as simple as a pointer to the database that is still using the Spanish version instead of making the switch the plugin is supposed to accomplish.
Again, QTranslate, who knows their own code, should be able to diagnose something like this very easy. I'm sorry to hear they haven't so far. Your solution is going to be either getting them to fix it or hiring someone who can edit PHP and MySQL (which usually go together anyway).