This Rollup fixes a “Bad Request” issue when accessing OWA through Forefront TMG. For a full list of changes, consult knowledgebase article kb2649961.
Note that along the lines of products like Exchange, cumulative updates for ForeFront TMG are now also called Rollup instead of Software Update or Update.
You can request ForeFront TMG SP2 RU1 directly from support here.
Source: EighTwOne (821)