I believe this just got answered for you in the General Discussion forum, but just for the sake of completeness I'll mention it here as well: this occurs when your GMs have an old/out-of-date copy of the retired.dat file. Check the box to include that file when you create your next league file, and the problem should go away.
Retired.dat only
needs to be included whenever player(s) retire, but as that can be several times a year (especially if you have multiple leagues with different end-dates for their seasons), I'd personally suggest including it in every league file. Until you have many seasons worth of history and retired players to worry about, the additional filesize (for my 17-year-old, 20-team, 3-level-of-minors league, the retired.dat file is currently only ~500KB when compressed) just isn't worth worrying about.
Please let us know if including the retired.dat file solves your problem so that we can close this thread out or provide more help if needed.
- Kai