unable to text ONE of my contacts

[kingfisher171]

I have a sony ericsson K750i mobile that I have used for ages. I have just discovered that if i send a text to one contact,(son-in law to be) it fails to arrive.

In SENT, the status of the text shows NOT RECEIVED. The phone number is correct as I phone the contact, he sent me a text and I hit the reply button, this shows NOT RECEIVED.

I've re-entered his details under a slightly different name, but the same number obviously, still with no luck

I've asked him if he has blocked my number and he say's not.

So, what can anyone offer by way of an explanation please.

Oh, I'm on vodaphone he is on orange and in the same room as my daughter who is also on orange and she gets her texts

[kingfisher171]

interestingly enough, seven message delivered texts have now come through, one after another. I have since text back with another, but it is being held somewhere as it hasn't arrived yet.