HI Hrvoje_86:
I also met this problem. Because the loading animation will stop in few minutes, but for some big sites the importing process will consuming more times. If the loading animation stopped, the importing process will be going on until it finished or the exception be throwed(You can find the exception log under "Cms_Data\WebEvents"). After the importing action finished, the page will be reload.
If your site very big(bigger than 200M), I suggest you to remove the files(images,videos,flash) from the site package, and then copy the files manually.
If the db data is too much(much than 50 thousands record), I suggest you to migrate your database manually rather than export/import the site.
Regards,
Jifeng Huang
Kooboo Team
Microsoft ASP.NET MVP