Originally Posted by ricocchet
I rectified this problem by conducting a hard reset.
Probably not the news you want to hear, but it solved the problem for me.
Well I thought about it but decided to contact HTC support first. They suggested that I backup all my contacts to my SD card then delete them all off the phone. I really didn't see how this would help since the person being linked to the messages wasn't a 'contact' he was just added to the People app by facebook.
Also another thing I noticed is that on facebook some people choose to put their phone numbers up which get put on the phone when you sync your facebook contacts with the phone. This particular person decided to be clever and instead of putting actual numbers they put things like 'Mobile: I'm not telling you' so the number was saved on the phone as 'I'm not telling you'. I decided to go in and edit these on the phone (cause you can't delete them) to just numbers i.e. '12345' so that none of his numbers were text.
Then in desperation I went and did what HTC recommended, deleting my contacts and restoring them and the problem was fixed!!!!
Unfortunately I can't confirm which of the 2 methods I tried actually work cause I did them without checking to see if they problem had been fixed in between.
So for anyone else with this problem. Check the person who the messages are being linked to, if they have text for their phone numbers, edit them to numbers (any numbers). If this doesn't work go to People>Menu>Import/Export>Export to SD card, then select all the contacts. Then in People go to Menu>Delete>Menu>Select all and confirm. Then restore the contacts by going to People>Menu>Import/Export>Import from SD card and that should do it!!