WSS 3.0 web part menu button not working after export/import

I have a wss 3.0 site exported with no errors,but when i import it (no matter to what site), the webpart menu button on the default page will not be working any more, as when i click on it, the drop down menu doesnt popup ( so i cant modified the view and etc.).
But if i create a new web part page on that imported site, the menu button works fine with the new page.

Any idea ?

[403 byte] By [DexterWong] at [2008-1-1]