They're OK here. on Mint Linux > Firefox > 3mb bandwith, [ Mizuki Hitoshi sample ] so it's definitely your connection.
I can't help, but I would bet it's JavaScript woes --- since it rarely affects all browsers, I Google looked that up since that's very unexpected, nearest I can see quoting from another forum:
Ordinarily, website JavaScript interpretation capability is incorporated directly into each browser itself as an 'engine'. If IE, Chrome/Opera, and Firefox all have such a similar problem, it implies that the different JavaScript engine designs used in each of those products is failing to operate correctly, which is extremely unlikely to originate within the browser engines themselves. When such different applications share a similar problem, the cause typically lies within something in-common ahead of or associated with all of those apps: an anti-malware application or setting, a router issue or setting, an OS security block or access limitation of some kind, or some kind of malfunction within the OS that blocks some critical JS execution steps.
blackbird 71 Opera Forums etc.
Updated