I update to Upgrade Pack 3 when it came out a few days ago. (I had recently install LMDE with Upgrade Pack 2 after moving from Julia.) Julia and LMDE / UP2 ran just fine and has since Julia came out. Almost everything in UP3 works fine too and I had no issues during the upgrade install. However...
Music and video playback has a long pause of about a minute before anything will start playing. Banshee is my normal music player. When I select a song to play, it does nothing for a minute before starting to play. Once it plays, it plays just fine. It will also go to the next song without any delay. That is true no matter if the song is just the next in the list or if shuffle is on. It only does the delay when I manually select another song.
The same thing happens when I play any video stored locally or inside the standard Chromium that same with UP3. In fact, I get this delay of a minute with any video or audio played with any tool/software. All other players that I have tried give me the same minute delay before starting.
I did see the message about errors with gstreamer, but I didn't get that or any error message during the install or during any playback. BTW, System Monitor is not showing any additional activity during that minute of time. i.e. I don't see any process that is running that might be the cause.