Thanks for posting your websites Cesarezzi.
Here's what I'm finding. When I visit your websites in IE9, they are forcing my IE9 to default into Quirks mode. This generally means there's code being loaded that is not exactly syntax correct (or a document that has been incorrectly declared in the header).
Also, my IE console is reporting an error with Mootools.js. Here's the error I'm getting in my IE9 Developer Console:
SEC7115: :visited and :link styles can only differ by color. Some styles were not applied to :visited.
www.filipesport.comSCRIPT5022: DOM Exception: INVALID_CHARACTER_ERR (5)
mootools.js, line 1 character 21432
SCRIPT5022: DOM Exception: INVALID_CHARACTER_ERR (5)
mootools.js, line 1 character 21432
I would suspect that either your top menu or your image slider (or both) are using some form of Mootools. Sometimes mootools.js does not play well with IE. You could try turning off some of your Mootools dependent items, and seeing if this makes a difference in that white loading screen. This would at least help you narrow down which extension is causing the issue.
Make sure to Shift+Refresh when you reload your page (to clear your browser's cache and get an accurate view of what's going on) after you turn different extensions off and on.
In any case, call me lazy, but the white blink in my IE did not last long enough for me to really notice it all that much. I'm not sure how big a deal this really is, but I hope this helps you down the "road of recovery".
_________________
Ryan
Numinous Productions
Custom Joomla Templates, Joomla Troubleshooting and Personalized Tutorials
http://www.numinousmedia.com