Rather odd problem. I'm on Version 2.2.6, and for some reason its giving me an error in the registration page when you first enter it. I'm not sure where the error can be found, but its defiantly linked to this hack. I have Microsoft Visual C++ installed that included a script debugging program that picked this error up, so maybe if you don't have MVC++ you may not even get the error on 2.2.6, but it's there I'm sure. Anyway, at first you can hit "no" to the alert, but then when you try to view your avatar on the forum homepage it does not show (in the welcome panel). From there I have noticed the users avatar does not show at all to themselves, but to others it does....
See attachment for picture of error, I hope you can fix it
edit:
Now that I overlook the error, a "runtime" error is usually cause from Javascript, is it not? That is the only other language used on my forum other than PHP/MySQL and HTML (which generally does not create those kind of errors).