I just went through the entire purchase process and it all worked for me. Is this on your live site or local that you are having the problem? Please provide more precise steps to reproduce the problem and I can look into it further. I can't fix an issue that I can't see.
The memory pool error seems like a server configuration issue. You would probably have to update your php.ini file to fix the problem like:
apc.shm_size = 64M
The shm_size value must be too small on your server.