If you use the command from Terminal:
curl -I
http://www.volatile-dev.com/LockCale...endar_0.3b.deb
it returns:
HTTP/1.1 200 OK
Date: Wed, 11 Feb 2009 01:13:08 GMT
Server: Apache
Last-Modified: Mon, 09 Feb 2009 00:28:54 GMT
ETag: "5000000036390-1796e-46271749b3d80"
Accept-Ranges: bytes
Content-Length: 96622
Content-Type: text/plain
Where curl -I
http://apt.modmyi.com/2debs/49ers2.1.deb returns:
HTTP/1.0 200 OK
Set-Cookie: ServerId=1218; path=/
Date: Wed, 11 Feb 2009 01:15:44 GMT
Server: Apache/2.0.63 (Unix) mod_ssl/2.0.63 OpenSSL/0.9.7a mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 PHP/5.2.5
X-Powered-By: PHP/5.2.5
Content-Description: File Transfer
Content-Disposition: attachment; filename=49ers2.1.deb
Content-Transfer-Encoding: binary
Expires: 0
Cache-Control: must-revalidate, post-check=0, pre-check=0
Pragma: public
Content-Length: 3361982
Connection: close
Content-Type: application/octet-stream
So, as far as I understand it (which isn't very far!), the volatile-dev server doesn't have the mime type set up correctly.
I'm not sure what the solution is, but if your end goal is to install the lockcalendar manually, you could download it to your desktop computer and SSH it over to the phone.