Why is my Internet Explorer 8 suddenly refusing to connect?

For the last few days I have noticed that in the early to late evening – after 8:00 PM local – when I launch IE8, it sits there trying to Connect with the progress bar not moving and showing a blank window. This is after a full day of launching and closing IE8 successfully. It is not my Internet connection as other PCs on the same router start up IE8 OK. If I restart the computer or just Log Out of Windows and log back in, IE8 again works fine. OS is Win XP SP3. I re-installed Internet Explorer downloaded from Microsoft last night, but this evening it stalled again.

Thanks for any suggestions.