I have the same problem.I have contacted with the host(hostgator) to increase the values of 1. memory_limit, 2. max_execution_time but they responed me:
I apologize but these are not limits that can be changed on a shared server. Since the server resources are being shared amongst all clients we can not allow each user to set their own limit. You would need to upgrade to a dedicated server in order to increase these limits.
I don't know what to do now?
Please help me!