IE9 won't work on anything older than Vista- IE10 will probably work only on Win7.

I've had issues with connecting/server not found when using the bookmark in Chrome/Dragon (though hitting refresh loads it real quick), but it kinda depends on the time of day. Might have something to do with the network traffic of your ISP...

Could also have something do with your a/v software- some like to inspect everything before you see anything. Also, the rendering engines of the various browsers load differently as well. Or you have multiple tabs in the background that are bogging you down. Or your PC is doing some scheduled task in the background that is using up your system resources- I've found a lot of the time when my laptop is acting sluggish, it's because it's doing automatic updates of various programs/apps.