Where/how does this message show up?
Lately, i have come across this error message, Disallowed Key Character when i login into some of my article directories or when i login to other software tools. Because of this, i cannot proceed with any action. Even in one, i ws logged out, i was denied access, and i am requested to create an account. I tried to Google the issue but did not come across any concrete action which would help me to solve.
I have read about this happening do to a cookie having a $ character in it. You might try deleting your cookies or at least the one(s) related to the site(s) you are having trouble with.
Website: Success With Money
"If your content doesnt drive activity or conversations, dont expect it to drive links." Tom Schmitz, Search Engine Land
Try clearing your browser's cache and delete all temporary Internet files.