I'm not sure if it is just my instance, but ever since I installed 5.4.3 all of the .onbody classes in the stylesheet fail to work properly. Text and links that are normally controlled by these options no longer work. In fact, the text and link colors default to the standard body and link colors. Is this due to the source code being changed?

Did you make any changes to your stylesheet at all when upgrading? Any chance you can post it here? If there is a syntax error anywhere in the file then it can keep classes below the error from loading properly.