im not sure, maybe the person you are trying to send it to isnt a member? also, how do you become a member? =D
Scarlet123: to apply for Full Member, you need to fill this form in and submit. Some patience is required--last I heard, processing times were taking more than a week. Empty Closets - A safe online community for gay, lesbian, bisexual, transgender people coming out - Regular Member to Full Member request
Is the person you are attempting to send a message to (I'm assuming it's a private message) also a full member? If not, that'll be why.
The person you want to Private Message should also be a Full Member in order for them to be PMable. Basically, PMs can only be exchanged between two Full Members or more. Alternatively, if you're referring to wall messages, some people have private walls which are only available to friends. I should note that staff members are always PMable regardless of membership status.