I just came across this information from Linda Hirsch at http://www.creators.com/lifestylefeatures/lynda-hirsch-on-soaps/lynda-hirsch-on-soaps-gossip-2007-09-22.html
This is the jist of the article by Linda Hirsch:
"Bold and Beautiful's" Susan Flannery (Stephanie) has asked the show for a medical leave of absence. Flannery has been suffering with fibromyalgia. The condition (we know of what we speak) comes and goes and comes and goes — like a bad relationship.
The interconnective tissue ailment is not fatal but has numerous debilitating symptoms. At its worst, "sleep" becomes the sufferers one and only hobby. Every muscle in your body aches, and even gripping a steering wheel or trying to applaud becomes an Olympic event.
B&B has granted Flannery's request. Her flare-up has come at an essential time in her character's storyline. Recasting Flannery even for a few episodes is not an option. So until Flannery returns, B&B will be Stephanie-light. Remember, it is a soap — so Stephanie can always do her evil behind the curtain.