Problem sorting in table

[aaa89]

Hi, I have a strange thing with a table I've built. When I click sort on columns that are numbers, I get "sort A to Z" as if it was text... I was playing around, converted the table back to a range, then back to a table - I noticed that if the table is less the 15 rows everything works fine and I get "Sort largest to smallest", as soon as I expand the table down one more row it changes and shows me "Sort A to Z".
Is this a bug? Do i have to rebuild the whole file? How to I get out of this mess?