About two weeks ago, there was a change made to fix the problem of email notifications not working for the majority of users on this forum. My guess would be that this coincides with the notifications no longer working for you. The change involved the reply-to address from the forum changing from
forum@ncrunch.net to
forum@do-not-reply.ncrunch.net. Do you think it may be possible that this change in reply address has somehow triggered a spam filter on your mail host? If you have another address you can temporarily switch to, perhaps we can test this to see if the messages a being thrown out.
Something else to check is whether your forum profile has its notification preferences set to something sensible. A big problem behind notification issues was that new user accounts were defaulting to having notifications completely disabled at a global level. I don't think your account was affected by this (as you signed up very early), but it may be worth a look -
http://forum.ncrunch.net/yaf_cp_profile.aspx.