A pain point with v1.3.9g has to do with some sanitization safeties added for security reasons.
Unfortunately there are some unpleasant side-effects whereby HTML code is rendered to display instead of being saved as intended.

A workaround is posted here: http://www.zen-cart.com/forum/showthread.php?t=165081

v1.3.9h will have a different approach which will make the whitelisting discussed in the above thread to be moot.