Just a wild guess, but I think your limits are determined by access level. My PM limit is 10,000. If you're a non-VIP member it's possible you have severely restricted limits since you're a non-paying member.
But that's nothing more than a mere guess. It could be a bug and an administrator will have to give an answer for anything to be definite.
"The devil I'll bring you," answered Hagen. "I have enough to carry with my shield and breastplate; my helm is bright, the sword is in my hand, therefore I bring you naught."