Other emails working, yes. Tried both PHP and SMTP. CB1.4, Joomla 1.5.23.
Yes, providing correct email address (as I said it works fine using the Joomla login module).
I've solved the issue by combining the standard Joomla lost credentials functions (together with the Reset Password plugin from Mark Totzke) with the CB login module. This is more elegant than the CB lost password/username functions anyway. Love CB, but this bit isn't a great user experience even when it works.
Thanks for your help.