I have had this phone for almost a year without a single problem. Today I have tried to send quite a log text message to a friend but the message doesn't go I just get a message on the screen saying "cannot send" without any explanation at all. I have downloaded the user guide and can find no reference at all to this message... All of my other text messages are sending ok. I have forwarded the message to my wifes windows phone, it arrived on her phone and has turned green which I think means it has been sent but no delivered message received yet. any help please. thanks

You says quite a log, (long),? message . As far as I know the maximum is still 160 characters or so. That may be the problem if it's substantially longer.

I seem to recall there is a setting which if a message is too long it will try to send it as an email.

perhaps you accidentally added the friend on the block list, happened to me on my Samsung Galaxy, sometimes the most obvious solutions are the ones we can't see, i hope you get it fixed

On some network/handset combinations, messages SMS which use multiples of the 160-character limit or have multiple recipients, or are replies to received MMS messages, are composed as MMS.
If you have available SMS allowance, but not "cash credit" required for MMS, it will refuse to send.

I don't understand much of what has been said but your suggestion seems the most likely but I am amazed that this problem exists on modern Windows phones.....It would help if there was an indication of what the reasons are for "cannot send" message was in the user guide on the phone or on the internet but there is no mention of it that I can see..

I split the message into 2 and it sent but what a pain....crap phone obviously thanks anyway