Okay, further to my last post, I did just find one thing interesting. The problem only happens when I right click the mouse to open in a separate window or new tab (IE 7). It's fine when I left click.
This is weird because I've had IE 7 since it came out, some time back, and have been right clicking to open in a new tab with no problems.... until about 2 weeks ago.
Huh?
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Edit:
Now I've found that if you click Ok for the Windows message that says address can't be accessed and then Refresh the window, it's fine.
I don't think this is specifically an IE 7 problem, as I'm finding I'm only having this business happening on A2K. Perhaps some settings have changed on A2K and are affecting those that have IE 7?
By the way, this is what the message box looks like: