As long as you have a bootable clone of your Snow Leopard system before you upgraded, no problem. And, if you have your SL installation disk, it can be done. If you have neither, it would be a problem since you do need to wipe your drive completely before "downgrading". You cannot simply install an older OS version over a newer one. So you'd also have to have a current backup of all your files because they will be deleted.
So, are you sure you want to do all of this or would you like to explain and troubleshoot whatever problems you are having?