We finally shipped the Rollup QFE, which fixes some ugly issues with Rollup 2, especially in countries with DVB-T service. If you're using DVB-T and Media Center, you really want this update.
If you have DVB-T service and got the "scrambled guide" bug manifesting on your machine before you could install this QFE, what you need to fix it is to reset your EPG data. The easiest way to do that is to go into Settings-->TV-->Scan for more services, click the Delete Existing Services button, and then scan. If you live in an area that can receive more than one DVB-T service that broadcasts the same program, you may still see "duplicates" in your lineup, but that's to be expected.
Even if you haven't experienced the scrambling bug, you should at the very least scan for more services, because we added a bit more flexibility into the scanning code to recognize transport streams with corrupt, missing or downright lying to us NITs (Network Information Tables). If you live in Italy or Spain, in particular, you should get the update and rescan.