I don't believe you can fix that problem. It appears to be an issue with the google API on IE6 and IE7 when centering on that point. You will see if you drag the map around it will show and then if you drag it back to center the gap will appear but it doesn't have problems in IE8 or FF. I'm pretty sure there is nothing you could really do to fix it on IE6 and IE7 short of center on a different point where the problem does not occur.