check your server php.ini settings

Following are values we use on our server

max_execution_time = 600
max_input_time = 600
memory_limit = 32M
error_reporting = E_COMPILE_ERROR|E_ERROR|E_CORE_ERROR
display_errors = On
register_globals = On
post_max_size = 800M
file_uploads = On
upload_max_filesize = 800M