I have version 5.3.1 version of conflunce.
When I load a space in IE9 I get a blank page if logged in. IF not logged in it shows the page correctly. In Chrome it works both ways.
Compability mode does not change anything.

view Source gives this :
<script language="VBScript" type="text/vbscript">
Function VBGetSwfVer
on error resume next
Dim swControl, swVersion
swVersion = 0
set swControl = CreateObject("ShockwaveFlash.ShockwaveFlash." + CStr)
if (IsObject(swControl)) then
swVersion = swControl.GetVariable("$version")
end if
VBGetSwfVer = swVersion
End Function
</script>