[HD2 General] MaskedMagi:
Just to add to this with my personal points of experience:

* Normally you can tell if the message has sent if you watch it for a few seconds after you press send and it briefly flashes, though I still always check the Outbox folder to make sure.

* Sometimes when you check the Outbox folder it has messages from other folders (such as your inbox folder) which is wrong, just keep switching from inbox to outbox to get the true view of the outbox folder.

* An indicator for some people is that there is a problem was the volume bar not showing up correctly in the music player when music was playing, also caused stuttering in the song (possibly due to the volume keys actually skipping the playing track forward or backward with each press?) Normally when this was observed it was a tell-tale sign that the SMS bug has struck again.

Solutions

(or more accurately, temporary work-arounds: think duct tape around a leaky pipe ;) )

There is NO final guaranteed solution that works 100% of the time for 100% of people, however here are the few attempts that I know:

1.) WORKS FOR ME EVERYTIME SO FAR*::

- Soft reset the phone (turn it on and off).

- Go to your outbox folder (options, view traditional mode) and open the unsent message(s). Select all and copy the message, then delete it. Start a new message, paste the text and send again. This works everytime for me, though it is annoying turning the phone on and off.

- If you have whole bunch of unsent messages in the outbox then open up word/notes program and repeat the previous steps, copying and pasting all messages that were unsent in the outbox. This really really sucks if you have a lot of messages that didn't send, which is why I always make sure to regularly check my outbox.

2.) Another less successful (it seems) is to change your network to GSM only; mixed response, doesnt always work, or if it does the problem comes back again anyway at some point.

3.) Go in to the settings and add +44 (i.e UK area code or whatever your country code) in front of your SMS number (the network number) - again I tried this and did nothing, mixed responses but in my eyes does nothing.

4.) Add +44 to the beginning of every number in address book: did nothing for me I doubt this is a solution.

5.) Send yourself an SMS to clear your outbox: I tried this twice, never worked for me

That's it off the top of my head, to conclude though the best method I have found is to simply turn it off and on and copy and paste then resend freshly composed messages.

The problem may not be there for ages, then suddenly hit your phone, dissapear, then come back. With my old HD2 it happened about 3-5 4 times a day, with me turning it off each time, with moderate texts (maybe 10-20 max a day). I received a replacement HD2 today and after sending about 6 texts I have not had this problem but this means nothing, I'm expecting it to rear its ugly head at any second...

*Note that when I say 'works for me every time so far' I am not saying that this is a solution to fix the SMS bug, merely that it is a workaround (albeit not a good one) that has worked every time for me so far. However there have also been reports of people turning the phone on and off and the message still not sending, though this may be due to them holding their finger on the message in the outbox and pressing 'resend' which in my experience hardly ever works. Deletion and resending the pasted message seems to be the best way forward, apart from disabling the HTC messaging app altogether that is...