Can't text some contacts

Question

I can't send or receive text messaging from all of my contacts.  I can call them but no text message.

Answer 1

I had the same problem with at least two of my contacts on my Droid 2. I believe I've solved it, at least for this particular case.
My example case is two of my roommates, both have iPhones, both on the same network, and I entered the same phone number formatting when creating their contacts. However, one of them, the one I can't send messages to but can receive from, has a linked Facebook account with a phone number formatted with a "+1" in front. That's the link between my working/non-working contacts, a linked Facebook account with a phone number provided.
The three stepper solution is:
1) Erase the manually entered mobile number ( it's possible, actually, that this is all you need to do).
2) Delete the conversation that has the failed/not-really-sent messages.
3) Send a text to that number (for me, formatted as 5035551234), at that point it will automatically link with the existing contact and continue working normally, using the properly formatted number as the default (I don't see another way to change it, but this is simple enough).
This was an interesting problem, because certain geographical locations (different cell towers) would allow sending for the otherwise poorly formatted phone number.
Hope this helps with what was an incredibly frustrating problem.
Cheers.