Happens occasionally. Send an email to 365support@strat-o-matic.com right away - they will clear it right up. Give them your league number or your user name.
Yes, it has happened to me on occasion as well. I use Firefox, and what causes this for me is when I have two SOM tabs open at the same time, one with the main team and the other with a clone "practice team" and I end up trying to drop players from one team when I'm still logged into the other team.
SOM will fix it for you, but it's best to contact SOM "help" first thing in the morning. Hopefully it will be fixed before waivers runs.