Yes, we introduced this bug with our cs4 updates. CS4 automatically greys out image buttons in interfaces until they are moused over. This caused us to move to images instead of image buttons in some cases to fix the way our UI looked. Unfortunately we later discovered that buttons change the focus on the field and images don't and DW doesn't update field values until they are blurred.
We will be addressing this problem in updates but many of our products may have this behavior until that time. Basically the last field you update may not "stick" unless you blur it by clicking into another field first. Most products we have recenlty updated have included this fix.