Error switching to ID files

lately I have started having problems when switching to a few of my ID files ( I have many for different location docs, and domains). When I switch to the location document I want, it prompts for the password for the correct ID file, but when I put in the correct password, I get:“Illegal null parameter to security function”

I can click OK on the error, then click CANCEL on the ID file prompt… but if I check File - TSecurity - User ID, it shows it DID log me into that ID file, but If I try to open any databases on the server… it still wants the password again.

any ideas?