Russianru, not sure that I understood your issue.
1. You log in as admin
2. You go to your main page
3. You get a blank page
4. If you go to any other page- everything is ok
5. If you log in as any other user everything is ok too?
We can't solve that problem without taking a detailed look from the inside. Could you please, send me your admin access details in the private message? Waiting for your response. Thanks