Will Norris et al’s WP-openid plugin error

Hi experts,
Recently, I installed the 2.0 version of Will Norris et al's WP-openid plugin, on WP 2.3.1.
Now I am having issue at the end of authentication loop.
When I try to post for WP Test 2.3.1 the following error message appears.
Would you please help me to resolve this error?
Any help would be appreciated.
Thanks for this.

Post to Weblog error.
Can’t post for WP Test 2.3.1 because the server reported an error: parse error, not well formed.
