I'm owning A TF300TG model and I recently tried to flash one of the ROMS referrenced on those forums and by doing so I found out that my tablet had lost the 3G features so I had to flash back the Asus stock ROM to get it back.
I had the same problem and I just issued the same command a second time and it worked just fine :)
Try to format your /system (under the mounts and storage option) from CWM and wipe data and cache.
AFAIK, this will wipe your data, remove CWM and uninstall root. Your device's bootloader will still stay unlocked though.
You will have to flash CWM back using this guide: http://forum.xda-developers.com/showthread.php?t=1668173