There are so many variables here that this could be alot of work and most likely isn't a Firefox issue. But, you can try the following: * Are both computers connected to the internet in the same way? Are both using wired or wireless, or is one wired and the other wireless? If they are both Wireless is one further from the router than the other? * Do both computers run the same security software with the same updates and settings? If not, double-check that. * On the troublesome computer, check that all your software (Windows, Flash, Java, Firefox, etc.) is fully up to date (you might have to check a few times) * Try to restart your router just to double-check. * Also make sure you test with a Fresh Firefox profile. [[Use the Profile Manager to create and remove Firefox profiles]]