3.1.1 Upgrade Broke Network Admin Access

There are quite a number of suggestions on this forum concerning “Page is not redirecting properly” and variations thereupon. The exact problem I have is this:

Auto upgraded to 3.1.1 from 3.0.2 Everything works except links to Network Admin and the temporary Update Network suggestion, both of which return the “redirecting” problem and finally fail, in Firefox and Windows Explorer.

All the sites running under this install are working.

Both of those links have the form of “https://www.mydomainname/wp-admin/network/” rather than “https://mydomainname.wp-admin/network/” as do all other links within the Dashboard context. However, modifying the addresses does result in gaining successful access to the network admin page.

I have taken these steps to try to correct this problem:

1. Deactivated all plugins;
2. Changed the theme to the default;
3. Deleted both .htaccess files;
4. Fiddled with the Permalinks but have not disabled same;
5. Manually reinstalled 3.1.1
6. Investigated the question of canonical links, to no avail and about which I am not entirely clear;

I have run out of suggestions and, according, am now looking for more. Any good ones?

Thanks in advance