This is because of NAT reflection. You have a few options.
Disable reflection in System -> Advanced
Change the webConfigurator port in System -> General
How can you fix this now? Do this from the console ( Option 8 ) :
pfctl -d
Now login and do one of the above options.
Once you are done, run this from the console ( Option 8 ) :
pfctl -e
Please click, "Thanks, Solved" if this fixed you're issue. Thanks!