unable to allow contacts to send messages to mobile device

when I try to edit mobile settings, the checkbox to "Allow people on my
contacts list to send messages to my mobile device" is grayed out- won't let
me check the box. Help!

I have the exact same problem.

Some help would be lovely.

After a few frustrating hours, I have found a temporary fix to this problem.
Hopefully it works for others!

Go to http://login.live.com/
Sign in. (I have my Gmail signed up for it.)
Click the Windows Live Messenger looking information on the top right
View your account
Registered Information
Make sure you have a country/region selected and hit save. (You may have to
agree to something, I can't remember now)

Sign into Windows Live Messenger
Add yourself as a contact to test this
Right click your name once you've been added and click "Enter a Mobile Number"
Once you've filled that out with your cellphone number, click save
Right click yourself again and click "Send mobile text (SMS)"

If it sends you your message to your cellphone, you can then tell your
friends to do the same few steps for you.

I hope this works for others!
Hoping for a better fix though soon.