I have every episode of The Big Bang Theory recorded. The first six seasons all appear in one group, but the three episodes that have aired in the newest season, season seven, are appearing in a separate group.
I went into the "fix artwork/identification" area and clicked the same show from the list of choices for both of the groups, but that didn't help.
I'm using version 1.9.1, but I noticed the problem in 1.9.0 and didn't have a chance to report it until now.
Re: New Series Recordings Appearing In Separate Group
Media Center sets a different ID to different series... for some reason that ID must have changed... so here is what you can do:
Open up Recorded TV HD Settings (outside of Media Center in the start menu)
Go to the Series Override tab
You should see two series listed there for The Big Bang Theory - select one of them and click Edit
You should see an option in the bottom left corner of that window to combine with another series
Use that and you should be good to go