Odd Root Server Issue?

[mofo]

Hey guys,

I have a very weird (to me) problem.  This issue was fixed, but I want to
know why it happened from someone who understands this better then I.  Here
we go.

I have the domain 'northroute.net' with DNS of icewall.vianet.ca
(209.91.128.10) and gwn.vianet.ca (204.187.88.10).  The MX for this domain
pointed to mail.northroute.net (209.91.181.2).

There is a domain 'ottawahostel.com' with DNS of ***mail.northroute.net
(207.210.113.4)*** and another server of no relevance.

Now here's the issue.  When I had northroute.net MX pointed to
mail.northroute.net with a local IP, my name servers reported the correct
IP, so did the rest of the 'net.  But then all of sudden, name server after
name server started picking up the mail.northroute.net as being the
207.210.113.4 which was the old server!  But why?  I had my A record for
mail.northroute.net pointing to 209.91.181.2!  It WAS working?  When I
created a new A record it would appear, but mail.northroute.net is
constantly poisoned.

Here's my assumption.  I think for some reason the ottawahostel.com name
server entries on the root servers of the 'net were causing bind on caching
servers of the 'net to be poisoned with the wrong IP.  This barely makes
sense to me since the root servers - a.gtld-servers.net for example showed
icewall and gwn as the authoritive servers for northroute.net. <sigh>

Ok so here's my fix.  I changed the A record on my servers (icewall and gwn)
to a CNAME (I know that's VERY bad to do for mail!) and pointed it to
mailhost.northroute.net (209.91.181.2).  This worked, until I took out the
CNAME yesterday.  It started to break again today.  I've since changed the
MX to mailbox.northroute.net and killed mail.northroute.net altogether.

Any ideas?  It works now, but I think there's a fundamental flaw somewhere.
Just because a registrar has a name server entry that differs the actual
authoritive answer, why does this happen??

Please let me know if I'm not making myself clear.

Thank you kindly.

-reid