I went to bed at 5AM, I woke up to find someone placed an order at 9:20AM... for free...

Sometime between then, all the prices for all my items in my cart which has only been online for 3 days are now magically 0.00

The individual items still have their prices when I edit the individual items. but when they're listed in the categories, they all say 0.00

I can't seem to change them back...

Is this a hack?
What can I do to change/fix this?

I'd appreciate any help.