For reasons unknown we are having an issue with some, not all, trades validating and completing invoices then receiving data from Valve invalidating the trade. This results in the invoice becoming incomplete or put back in a pending state. If you are one of the unfortunate ones who has been put into a negative balance compliments of this issue, it will prevent you from trading. We reassure you we are looking into this issue and will rectify all valid trades as soon as possible. Your patience is appreciated.