Trying to Buy All the Runes, Error message?

I'm so close to buying all the runes and i am getting an Error message saying "An Error Has Occurred" "You have attempted to purchase or already own more than the maximum amount for this item." this message comes up no matter which rune i try to buy and which ever quantity. I wasn't even aware of this maximum, so now i can't get runes that i find to be more important that others that i have bought. i feel cheated...