I have a very strange problem with Mail...

1st of all when trying to compose a mail, it all goes well untill I use a space or return, then the cursor disappears. I have to click back in the message to type again and sometimes even that doesn't work.

So, I'll try copying in text from word for now, I thought, but the 'send' button doesn't work either! It just depresses and nothing happens.

No other program is affected, I can receive mail fine and I have never seen a program act so oddly.

Things I've tried: Clearing the font cache with 'Font Nuke' and using AppleJack, dropping com.apple.mail.plist on to the desktop to reload Mail.

Any ideas? Has anyone ever seen this before? I'm not gonna have to re-load OSX am I?

Thanks PB