Maybe its a cue file that you are looking at? Although, you have been using it for years and I'm sure you know better.
Sometimes iTunes seems like it has a mind of its own and sometimes does weird things. At least for me, anyway. Try ripping to a different folder that has nothing to do with iTunes. If that works, then you can just transfer the music to iTunes.
It would be a good idea to check how all of your software is configured. Sometimes, when programs get updated, they need to be re configured.
Sometimes iTunes seems like it has a mind of its own and sometimes does weird things. At least for me, anyway. Try ripping to a different folder that has nothing to do with iTunes. If that works, then you can just transfer the music to iTunes.
It would be a good idea to check how all of your software is configured. Sometimes, when programs get updated, they need to be re configured.