Hi Bhavin,
The issue doesn't seem to be PC dependent. If the same works proper on IE 9 and above on the same PC and also on chrome, this definitely is the problem with IE version.
As per your pt 4- When the same is loaded, try to find out from the debuggers, if the theme is loaded properly. There must be some setting options in IE8 of that PC to restrict the theme/css
Hope this might give you some pointer to proceed.
Regards,
Atul