Macbook Pro won't sleep with Express Card in Slot

[m021478]

Anyone have any idea why I apparently cannot close the lid of my MacBook Pro when I have my newly purchased Transcend 32GB SSD inserted into the express card slot?? Trying to do so only results in the computer attempting to reawaken itself periodically every 30 seconds or so (meaning that the light illuminating the Apple logo on the back of my Macbook Pro turns does initially switch off when I close the lid, but then it switches back on every 30seconds for a second or two, at which point I also here the DVD drive of the computer makes the 'eject noise' ~ as if it's trying to reawaken itself every 30 seconds or so...