The Info tab of any ARIA Instrument lets you to set the amount of RAM allowed for pre-caching. the 64bit version will let you select up to 16GB. 

This setting becomes the default for both 32 and 64 bit versions and if 16 GB is chosen, it prevents the 32 bit version of playing any streamed sound although everything else seems normal. 

If you inadvertedly set the max RAM to 16GB, Please update to the latest ARIA Engine.  Otherwise, you will need to reset the settings by erasing the default.aria file in either of the the following location, depending of what player is installed on your computer:

C:\Users\your user name\AppData\Roaming\Garritan\Steinway\

C:\Users\your user name\AppData\Roaming\Garritan\Aria Player\  

C:\Users\your user name\AppData\Roaming\Plogue Art et Technologie, Inc\chipsounds\

That way, your ARIA instrument will revert to its default settings.