Wiki, virtual hosts, port mapping, and frustration

I am a learning admin, and generally try and work through things myself until this time. I am pretty sure I need some suggestions.

I'm running an xserve 2x2 xeon, with a fully updated leopard server. I am not using postfix (I've switched to Exim), but my problems are surrounding what many server operators here may be doing... virtual hosting and trying to get all the services started...

Now I won't get into Kerberos in this post... as that's an issue between me and my ISP for not giving me either cname or rdns service (a beef I'm pursuing)..

So what am I doing...
1) one internally facing port 192.168... offering AFP and iCal service.
2) external port (wan side - but not fully reverse dns qualified) serving Web, FMServer, Wiki (trying) and Mail (exim) and a PHP based fileserver.
Notes on external port: I use dyndns to map all virtual domains to the right ports on my server. for example, domain1.ca is default 80, domain2.ca is 81, domain2.ca is 8081, domain4.ca is 8082 and so on. There are several. I pay for DynDNS to offer reverse DNS service to me by setting my server to only use their rDNS services (not including dns running on the server for the domain1.ca only which is the default).

The problem:
The main domain for everything works. Wiki works, user blogs works, mail works for all domains (separate from Apples anyway), iCal works fine, Open directory on the server runs fine (however without Kerberos - changeip still picks up ISP's cname for IP). What DOESN'T work... is the Wiki for all the port shifted domains. So any domain not on 80 doesn't work.

I can get the domain wiki to show on the wiki home page, but when clicked get the "404: No group with that name (domain2) hosted on this server" message. Even if I ensure the correct URL path is used.. still the same error.

Do I need to do something special to get the port shifted domains to work on the wiki?
All other aspects for them works fine, including realm access set through OD.

When I blank out the domain in the admin->sites-> for say the port 81 site it works. I of course can't leave it like this with 10 + sites.... and they can't all be blank.
So what am I missing here... a bad DNS entry that leopard is picking up on?

THe way dyndns works is the www.domain2.ca is actually mapped to www2.domain2.ca:81 and is cloaked so the user only sees www.domain2.ca in their browser.

Thoughts anyone. I know I'm pushing the envelope, but this seems like I'm just missing something I've overlooked here.

Thanks in advance.

Chris