Lately, I've gotten this error on both my laptop and my computer:
Cannot open registry key for install path of PlayOnline-compatible software
ID=1000
hitting ok gives another screen or two, one saying something about being logged in with Administrator rights.
I'll try to grab screenshots next time. I scanned with AVG and nothing turned up. On both laptop/computer, I did the thing where you copy files from a previous install, do registry magic and you can play. Starting up POL again, works fine, but that was similar to the previous virus I got with the "No such interface supported" error message.
Edit: Screenshots:
http://i127.photobucket.com/albums/p...x/hacked-1.jpg
XI Wiki

