Hello, I purchased 2 ink cartridges today for my Canon Pixma MP780 printer at Office Max. They were generics carrying the Office Mx label but were designed form my printer. The physcail shape and size of each cartridge was identical to that which was empty and I removed. However, it won't print and I keep getting the warning sign (Wrong Cartridge). I have followed the corrective procedure offered, to no avail. Any suggestions?