Well it works now, only because I tried every possible combo to make it work.
The problem? 2 problems actually.
1) I was using mydomain.com instead of blah.dreamhost.com to point to my calendar file within Mozilla. Anybody know why a straight forward wouldn't work? It isn't cloaked or anything. Even tried the allow linking from domain in the WebDAV settings.
2) I copied my calendar file into the calendar folder then enabled WebDAV on that folder. Apparantly that only allows read access to the file, you can't write to that file using Mozilla (even if I mess with permissions before enabling WebDAV on that folder). So I emptied the folder, enabled WebDAV on that folder, then published the file into that folder. Write works on it now.
Anybody know how to fix #1? I'd rather use my own domain than blah.dreamhost.com. Thanks.