Trouble accessing a Custom .dtd

I have created a custom .dtd file <http://bipolarworld.vianet.ca/HTML401-strictplus.dtd> and a test file <http://bipolarworld.vianet.ca/test2.html> to test it. When I try to validate it using W3C's validator <http://validator.w3.org/check?uri=http%3A%2F%2Fbipolarworld.vianet.ca%2Ftest2.html&ss=> it tells me that:

| Error: could not get "/HTML401-strictplus.dtd" from
| "bipolarworld.vianet.ca" (reason given was "File Not Found")

The WDG validator <http://htmlhelp.org/cgi-bin/validate.cgi?url=http%3A%2F%2Fbipolarworld.vianet.ca%2Ftest2.html&input=yes> gives me a similar result, without explicitly saying that it did not find the .dtd file.

There are only two things that I can think of that will cause this:

P1 - The ViaNet server is refusing to send out the .dtd file.

P2 - The validation sites are not getting, or accepting the .dtd file.

Here are a few things we tried, but didn't work:

S1 - A shorter file name. We didn't think this was the problem because UNIX allows very long file names, but it had to be ruled out.

S2 - Placing the .dtd in the cgi-bin.

S3 - Put the <!DOCTYPE ...> all on one line. Again, we didn't think this was the problem because white space is ignored, but it also had to be ruled out.

S4 - I asked the administrator if there were any restrictions on certain file types. He is certain there are none.

S5 - I added a link to the bottom of test2.html:

   <A href=
      "http://bipolarworld.vianet.ca/HTML401-strictplus.dtd">
         HTML401-srtictplus.dtd
   </A>

Clicking on the link downloads the .dtd file

S6 - I uploaded test2.html to another site <http://www.crosswinds.net/~bgiroux/test2.html>. Clicking on the above link from crosswinds-test2 will still download the .dtd file from the ViaNet site, but the validator still can't access it.

I am perplexed. If anyone has any ideas, I sure would appreciate it.

--
Brian P. Giroux

cc: www-validator@w3.org
    news:comp.infosystems.www.authoring.html