I was not seeing the Google Map tiles in Internet Explorer 8, so I tried to reproduce the error on a fresh D7 install. As the map displayed without any flaws initially, I added feature by feature that I had in the broken map. Strange as it may sound: the reason was that I was using custom graphics.
I have not really a clue why this happens - but I hope this error description here helps.
To reproduce, install D7 minimal profile. Create a Map Page View and add custom graphics. When viewing the map in IE8, you do not see the Google tiles.