I've gotten a couple of reports from commenters on my blog saying that when they try to use their OpenID, they get a "white screen of death".
I tried it myself, and here's what I observed:
Submitted a comment using my OpenID (http://dougal.myopenid.com/)
Got a 'blank' page (from my server)
View source reveals that it started to render a page, but stopped somewhere in the
Hit my back button
Didn't change anything, but just hit submit button again
Properly redirected to the myOpenID server.
I'm getting a fatal error in my logs from the Contact Form II plugin when it happens, for some reason, so it may be related to that, somehow. I'll dig in some more and see what I can find.