To reproduce: run Confluence behind an IIS 7.5 Application Request Routing (reverse proxy)
which rewrites requests to http://my.confluence.domain:80 to http://localhost:8090 – then set up a Trusted Application in another app (for example JIRA Linker Plugin).

When the app attempts to make an XMLRPC request to Confluence, it receives a 500 Internal Server Error, and the following IPAddressFormatException in the atlassian-confluence.log logs:

 com.atlassian.security.auth.trustedapps.IPAddressFormatException: "0:0:0:0:0:0:0:1" does not represent a valid IP address

Also, IPv6 addresses cannot be added to the Trusted Application Details in Confluence.

Full entry attached in log.txt