What time of year is your league at? Specifically, did any players retire recently (happens at the end of seasons and the end of each calendar year)? The player links can get messed up in the way you describe if you don't get an updated retired.dat from your Commish after retirements occur. Since retired.dat isn't included in all league files automatically (it's optional), it can be easy for a Commish to forget to include it the couple times it's actually necessary.
Let us know if that helps.
- Kai