What are the specs of your 3 PC's? I can't figure out a pattern.
My company provides a web service to lots of retail stores and we probably have 20 customers who all suddenly spotted this issue on our site.
Seems like half the support requests we get are for this issue. We just tell customers to download Firefox at this stage.
Seems to relate to some embedded videos loading in our case. I can't replicate in any environment I set up. Have remote access to a few.