Flash in tabpanel makes IE "Not Responding" when tabchange

[kyleSencha]

I use tabpanel(Ext JS version is 3.3.1) and flex in my website. When activing a tab, I create a panel in the tab to show some content. Some tabs contain flash components in the panel.

There is a problem when I do the operatings as following(for example, A is a tab with flash component and the flash component has scroll bar itself):
1) Open tab A and an other tab B.
2) Navigate to A and drag the scroll bar to leave its original location.
3) Navigate to B.
4) Navigate to A again.
When I reach the fourth step, IE will stop working for a few seconds("Not Responding" most of the time). Then IE returns to nomal and show tab A, and the scroll bar goes back to its original location.

To solve an other problem, I use following listener in Tabpanel.
'beforetabchange' : function(tab, newTab, currentTab)
{
document.body.focus();
}

Unbelievable，this problem is resolved. When I reach the fourth step this time, IE shows tab A quickly and the scroll bar stay at its location after being dragged.

This problem is resolved, but i don't know how it work.

Is there anyone can tell me why?

[WesleyMoy]

The code snippet you included seems to JavaScript code. Are you asking a question relating to Ext JS? This forum is for reporting bugs related to Sencha GXT. If this question was meant for an Ext JS bugs forum, please let me know which version of Ext JS so I can move this thread to the correct forum.

[kyleSencha]

Sorry, my question is related to Ext JS and the version is 3.3.1.
Please move it to correct forum. Thank you!

[WesleyMoy]

Thread moved from Sencha GXT Bugs to Ext 3.x: Bugs.