I spent (most of) yesterday upgrading from Mint 4 to 5r1
Did you perform a clean-install of Mint 5? Or, did you do one of those dist-upgrades? That might make a difference in your resulting stability.
There are also some differences in how sound is handled in Mint 4 versus Mint 5. The massive amounts of updates are not unusual for a fresh-install. That just means the distro is very active.
You may wish to open and verify your volume control settings. I am still a bit shy of the Pulse Audio, but I am reading up on it. Good luck, and please post back with your progress.