IF you're a Mac user like me, DO NOT UPGRADE to Quicktime 7.3 and iTunes 7.5 unless absolutely necessary (like if you're using an iPhone or have Apple TV, etc.). Idiot that I am, I got suckered in by the software update and after uploading the new versions of these software, am now unable to stream my favorite Virgin Radio Groove station on iTunes, nor have I been able to watch newscasts.
So far the problem seems to be limited to the Firefox browser and I followed all the suggestions on various threads in the Apple forums regarding these new software versions but have not been able to get them to work properly. Like if I try to access a video on YouTube or Reuters, all that appears is a white screen with the blue Q and question mark in the middle. No video plays, even after I've repaired the disk permissions, and restarted as had been suggested.
So I've gone back to Safari 2 for my browsing. All you need to do is download the latest Adobe Flash Player, Real Player, Perian, and Flip4Mac, repair your disk permissions, then restart everything. After that, your softwares will work fine and you'll be able to stream video seamlessly. (I just don't like using Safari because some web pages, like the new Yahoo, still isn't accessible on this browser. So you're stuck with the Yahoo classic version. Other than that, it's a great browser especially for RSS feeds.)
Oh, I've read that even Windows users are having problems with the new iTunes and QT versions as well so be advised to stall your upgrades until Apple releases its security updates or bug fixes.