Orange has a habit of delaying sms, I once sms my brother to test on the delay, it was 45 mins after I texted him then he got the text. Also I found that when you send a text in a weak single area it is most likely being delay from my personal experience.

Unless you are willing to pay 1p per text to orange to get a proper delivery report, then there is no actual solution to this i am afraid.

 

There's loads of posts about this on the forums already take a wee look ...It's not Orange, I'm on Vodafone, all the desire hd's are doing it since the update around new years, its a joke it hasn't been fixed yet, the only solution for now is get an app called sms alert, I've been usin it for a month and so has everyone else I know who has desire hd...