iMessage Not Working

[MikeM87]

Hi Guys,

Everytime i try to send an iMessage to another IOS5 device i just get the message "Not Delivered".

Has anyone else had this problem? I'm on O2 dont know if its anything to do with the data settings but my 3G seems to be working fine

Thanks for any input

 

[nooaah]

Is iMessage set to "On" in settings (under Messages) for both devices?