UPDATE - This has been fixed in Service Pack 1
Here’s a nasty little bug I found when editing families with type catalogs in 2012
Steps to reproduce:
Open a family that has a type catalog (W-Wide Flange is a good example) there is only one family type to start with in this family. Save the file. Now if you look at the family types all of them from the type catalog are in the family. At this point if you save (note that the ootb families are set to read only so you need to change this first), close and re-open the family the types go away and still left with one type. But if you change types to something besides W12x26 and save the file ALL of the types are saved in the family.
The development team has acknowledged this as a problem and said it requires a ‘code fix’ and can give no time frame of when it will be fixed.
My advice is to temporarily rename the txt file while editing your family so it doesn’t see it and ruin your day.
Support’s advice was that your library should be read only so this shouldn’t be a problem, that’s all good and fine for end users but when you’re editing the family it can become an issue.