Can't purchase any more runes!

I have been experiencing this problem and haven't been able to purchase any more runes for about 3 months now and was wondering if anyone can help. I have plenty of ip right now and have purchased about half of the runes in the game. When I try to click on the runes to buy them when I click purchase it says "An error has occured, you have attempted to purchase or already own the maximum amount for this item". I don't have these runes purchased yet and am only trying to buy one and not an amount large enough it wouldn't let me. Any ideas on what to do? I've tried re -installing and it hasn't helped, I've even tried other computers and they wont let me purchase them on my League account either :(