Mikrotik Web proxy from outside.

I am running web proxy on my Mikrotik using it to block websites. I need the students to be able to connect to the library database from outside my network so I need the proxy server to redirect the traffic that comes in from outside and goes back out using our registered address. We used to do this a while back using ez proxy but i figure since we installed a mikrotik we should use it. When the student enters the following address…

http://70.167.51.34:8080/login?url=http://www.lexisnexis.com/us/lnacademic

They get the following error…

ERROR: Unauthorized

While trying to retrieve the URL http://70.167.51.34:8080/login?url=http://www.lexisnexis.com/us/lnacademic:

There is a loop in network for HTTP traffic. Check your network topology and proxy & firewall configuration
Your cache administrator is webmaster.

Generated Mon, 06 Aug 2012 13:35:45 GMT by 10.0.0.1 (Mikrotik HttpProxy)

So I know they are getting to the proxy server but it is not going out from there.

Could someone help me figure out what i need to do to get this working?