Mobile Messaging Loss of functionality/providers ?

Hello,
I am based in the UK and use the Mobile Messaging function of
Windows Live Messenger to send text messages when people are not on-line. I
was using this function until last week, I sent a text on both the 6th and
7th of November successfully. Since Tuesday the 13th I have not been able to
send a text to the same number, the sevice provider for the mobile phone is
Orange, and as far as I can see from the various Microsoft Websites I have
visited, Orange is supported. I have checked my billing and have 18 text
messages left, so it is not a case of running out of credit.
Is anyone else having this problem ? is it a change in the service and
Orange are no longer part of it ? or am I just being unlucky ?

Thanks in Advance for any information.