Just thought of something are you putting the Rom file on the External SD Card the tablets internal Memory is also called SD Card.Here is where you find the external card.
/mnt/external_sd/ = SD card which is accessed by CWM
Also some cards dont work properly with this tablet so if you have a spare card or one in your phone you could back up the contents and format it Fat or Fat32 and try that one.
Also something I do is I extract the rom file onto my desktop just to make sure it isn't corrupted before I try to use it.Then you can delete the extracted files. That lets you know if the rar or zip file is complete.