Domain Mapping IP Address

The domain mapping plugin works well except for one issue.

My Wordpress 3 MU install is using subdomains for each additional website.

So I have my domain.tdl.
site1.domain.tdl
site2.domain.tdl
site3.domain.tdl
site4.domain.tdl
site5.domain.tdl
Etc.

I found that if I typed in a subdomain that didn't exist, (nositehere.domain.tdl), it would redirect me to http://domain.tdl/wp-signup.php?new=nositehere which is the signup for with "nositehere" already prepopulated in the Username field. Pretty neat.

However, after installing domain mapping, when I try and visit my IP address (http://173.xxx.xxx.xxx/), it redirects me to http://domain.tdl/wp-signup.php?new=173.xxx.xxx.xxx with "173.xxx.xxx.xxx" already prepopulated in the Username field!

http://173.xxx.xxx.xxx/ should redirect to domain.tdl...
not redirect to http://domain.tdl/wp-signup.php?new=173.xxx.xxx.xxx

Please help!