The bug has been archived in IE8 issue list since beta times. The only known workaround is to force IE8 to "IE7 combatibility mode".
Investigating Microsofts own code reveals that even they have not found any other workaround. You can find in the head section of Bing maps:
<meta http-equiv="X-UA-Compatible" content="IE=7" />
And in maps.google.com:
<meta http-equiv=X-UA-Compatible content=IE=EmulateIE7 />
Those tags make IE8 behave more like IE7 and cure the click coordinate issue. If someone is really interested what they actually do, I would recommend starting from this excellent study. What I learned about that article, is that the tag will not pass HTML5 validation.