Hey Igor,
This is usually caused by your server/PHP configuration.
Please make sure that in your PHP Settings (php.ini) you have the "memory_limit" set to 128M and the "max_execution_time" set to "900":
memory_limit = 128M
max_execution_time = 900
If you login to the Admin Panel (I suppose you can access it), set the "Error Reporting" to "Maximum" and then refresh the Homepage. If you get the following error, it means that you need to increase the above PHP variable:
Fatal error: Allowed memory size of 67108864 bytes exhausted…
If you are not sure how to increase the PHP settings, just contact your hosting support and they will assist you with that.
Let me know how it goes