Well importing language strings is part of the install so no issues there that I see.
The things that would prevent login all depends on what error you get.
If you run the install and on config specify the proper vb4 database info vb
license number not customer number and go through select external install select vb4 and fill out the proper vb4 info asked and then next step integration options set proper paths urls and turn on the integration you should be able to login and be integrated.
I have a copy on my vb4 site so I know it works. Are cookies set correctly
cookie path /
cookie prefix bb
cookie domain .yoursite.com
If so the login should work. you can post a test login and url for me to try out if you want