As of a few hours ago, the OnEarth server is down. That might be causing some troubles, but not a D3D device reset error.
Is this your first install of TopoFusion, or have you been using it for a while?
You might try deleting your TopoFusion.ini file. That will reset your settings to default.
Otherwise, it sounds like a video driver problem. Try updating your video card's drivers, or post your TopoFusion.log file here -- it should give us some clues as to what's going on.
Thanks.