[tx_dbs_tx]

You need to mount your sd card to your pc via usb as "removable" drive then check he properties of all the folders. Look for the largest folder sizes and then check the files inside those folders to see what's hogging up all your storage space. Simple process of elimination basically. If you don't see any obvious large files/folders then i would backup all the files you need to keep and then format the sd card with your phone. After formatting the card immediately check the storage card's capacity to make sure it is reported accurately and that there are no problems with the memory card itself. Then put the files/folders back once you have verified the file sizes are accurate and none are corrupted, etc. Personally I would keep only one nandroid on my sd ard at a time. You are doing this already from what you already said and that's good. Good luck