Why are you running 32-bit VEP? You should be running the 64-bit version so Play can run as 64-bit, not much point in having 12Gb RAM if you are in 32-bit mode. You can run the 32-bit VEP server, so that 32-bit programs (like Sibelius) can access the 64-bit plug ins.
Your problem is likely to be to do with 32-bit vs 64-bit mix up