What steps will reproduce the problem?
1. Attempting to log in to one wpOpenID, from another
2. Input openid url in either login or "Your OpenIDs"

What is the expected output? What do you see instead?
Expected; OpenIDs linked
Actual: "Error: Could not discover an OpenID identity server endpoint at
the url:"

What version of the product are you using? On what operating system?
Both wordpresses: 2.8.4
Both OpenID plugins: 3.2.3

Server 1
Apache version  2.2.11 (Unix)
PHP version 5.2.9

Server 2
Apache/2.2.4 (Linux/SUSE)
PHP Version 5.2.9

Please provide any additional information below.

On checking my access_log from the provider wordpress, I see HTTP 406's
coming from the requesting wordpresses IP address

Testing both login's with http://openidenabled.com/resources/openid-test
works and log's in fine, as does logging into both systems with a third
openid (i.e. google)