Element Delvalle

Hi guys, I'm trying to edit listings of mine in the marketplace but for some reason everytime i go to 'update' it comes up with an error: '1 error prohibited this product from being saved There were problems with the following fields: You must choose a category for your product before it can be listed' now i can understand this if i hadnt chosen a category... but i have, i've even tried different categories. nothing works. it just keeps giving me this error... i dont know what to do, if i cant update the listings then i cant sell them.. someone please help :(