This error message means you have gone above the ARIA Engine’s max allocated RAM allowance. This can affect any Garritan library or combination of Garritan libraries.
NOTE: "please consider the 64bit version" part of this message can be confusing, as you are probably already using the 64bit version of your player, but you're still out of RAM.
To get around this issue, you’ll need to increase the Max Engine RAM Allocation setting from the Settings section found on the right side of the ARIA Player or on the top of the CFX Players. After altering this setting, load your patch again.