Hi Bspraetz and ScottTDallas,
This seems to be an issue with the web browser that you are using to connect to the Slingbox, in this case IE8, but, have you tried to use a different browser like Firefox? Do you have the same issue?
I recommend to reset the plug in, this should fix any issue with the browser. Have a look at this,
Hope this helps
Tried FF, same problem. Removing and reloading the plug-in had no effect either. I have discovered that I don't actually have to reboot to restore funtionality of the Sling Player after the web-based access fails out. Repairing my internet connection fixes something that the plug-in seems to break or confuse.