Perhaps this is limited to the specific case, but anyway: for the Leagues - Top Stack Exchange users per week, month, quarter, and year page clicking on best this week userpic for SQA resulted in that lovely panda:
The only special thing about the user - it's SQA user:1 Nick Craver, and his last and only rep change is +100 (must be association bonus) on May 3, 2011.
Random checks of about 20 similar links did not reveal any issues.
Testing environment (for the record):
Win7 Ultimate SP1 x64 / FF 18.0.2
QA at your service.