CWM 126.96.36.199 and up allows you to choose your backup format. If you go to backup and restore, you will see the option. Selecting "tar" format will give you the backup format you are familiar with.
I suggest you delete the entire clockworkmod directory, then go into recovery, select the default format you want, then rerun your nandroid backup. Once you select your preferred nandroid format, stick with it.
If you use CWM 188.8.131.52, it should now be compatible with JB 4.2
Maxwell was the first "Smart" phone user.