We just completed a migration of a multisite WP installation, and I found that the original developer built the site on "site.us" before transferring it to "site.com". Since then, uploaded content like pictures link to "site.us/wp-content/etc" even though the domain redirected to "site.com". I did a seach and replace throughout the database for all occurences of "site.us" and replaced them with "site.com", then went though the wp-config.php file and other files doing the same S&R. Everything seems to be good, except for some reason, now the main sites admin screens link to "site.com//wp-admin" with TWO forward slashes after the domain name. For the life of me, I cannot figure out where this came from. I didn't include any slash in any of my search and replaces, and I didn't add a slash to any of the blog settings or network settings or site url or anything. It seems to have just appeared.
Also odd, only the main site exhibits this problem. The four other sub blogs a.site.com, b.site.com, etc all do NOT show the extra slash. FWIW, the main blog has a custom URL, and one of the sub blogs has a custom URL.
Any thoughts / solutions?? It seems to interfere with being logged in as an admin, though for the most part, the site actually behaves normally, even though the public sees the extra slash, too.