Before using a persistent encrypted usb flash drive running Kali 1.08 on your computer, we suggest you first test an unencrypted version for a few days. If the operations you are conducting work then try the encrypted version.
We found that when running the encrypted version on some computers, the usb connection to the wifi reciever was lost and many times files were not saved. Furthermore, to get some bash script files to function we had to write in sleep commands to slow the routines down or error messages occured.

We think this has to do more with computer speeds rather then any problem with the kali-linux 1.08 encrypted approach.