Problem with multiple installations

When you installed wp did you use the same database and if you did, did you change the table prefix in the second installation.

Resource:
http://codex.wordpress.org/Installing_Multiple_Blogs

This is more of a server setup issue than wordpress. You need to get your virtual hosts working first. Just put a simple index.html file in each vhost directory until you get the issue worked out then install wordpress in both directories, I know it works fine because I’ve setup 5 virtual hosts on a CentOS server.