A couple of things to try...
Under Settings>Playback>Volume Limit, you could lower the limit to something more comfortable. Or, if you notice that some songs are okay, while others are too loud, you could go to Settings>Playback>Sound Check and select On, which will help normalize things so all your music is near the same volume level.
If this really is an oddball issue directly related to the update, you could try Restoring your iPod via the iTunes Summary tab. That will erase everything and reset all settings and then reload songs, etc. from your computer afterward.
Hope that helps a little...