[Opserty]

I presume vb_user is the vBulletin User table correct?

If so your query won't return no matches because you will first have to hash the password so you can compare them. Here is a quick outline of what you need to do:

1. Connect to the Database
2. Fetch the Username, Password and SALT
3. Hash the input password and then hash it again with the salt.
4. Compare the input password with the Password you fetch from the database
5. Then do whatever you need to depending on the result.

With regards to your actual question, I don't think Passwords are case sensitive however I'm not too sure about Usernames but I think they are case-sensitve too.