I also experienced that, however In my case, I'm sure it was caused by a glitch. During the Osgiliath extra mission, Eredan would fire his bow fully automatic with an insane fire rate, however I didn't have infinite arrows, so I would empty my quiver within a second or two.
I were running the trainer when it happened, not sure whether the trainer might have provoked that glitch or not.
Anyway, the add XP functions just fine, I instantly ranked up to lvl 40 so not sure what went wrong in ur case.
I had the same issue and it turns out that it is caused by IE10
Pwizard has written a guide on how to remove IE10 search the message board for:
Reverting to Previous URLMON in Win7
That worked for me perfectly.