You cannot connect to the TC using a local IP address.
Read the details for setting up remote access.
http://www.stratospherix.com/support/gsw_timecapsule.php?page=6remote
You must use a global address via a dns service or have a fixed public IP ..
And the setup of the TC must be exactly right. It cannot be bridged in this setup..
If you have a router in front of the TC you will need to do the port forwarding in it.. so you translate 20445 to 445 and use a fixed local IP for the TC.
What we need to know is all the details of the local setup of the TC.
Perhaps give us a screenshot of the setup from your home LAN.