Could you elaborate on that a little? I have two Google accounts, both on different Apps domains, and I have no trouble using multilogin support with G+ on either.
To help debug:
1. Does multilogin support work at all for you? In other words, can you open both accounts' GMail in side-by-side tabs in the same browser? (The URL should contain something like "/a/something.com" or "/u/0" in each one.)
2. In the first of these tabs, if you click the +You link in the upper left corner, does it take you to G+?
To help debug:
1. Does multilogin support work at all for you? In other words, can you open both accounts' GMail in side-by-side tabs in the same browser? (The URL should contain something like "/a/something.com" or "/u/0" in each one.)
2. In the first of these tabs, if you click the +You link in the upper left corner, does it take you to G+?
3. Same as #2, but with the second tab