There's two ways to look at it: no, there's not a bug in U59 audio fix because my client and many others do not have any problem whatsoever and yes, there is a bug in the fix because a some do crash. And, yes, there were system freezes on 64b before U59. I assumed these were due to my sound cards rather than purely a DDO problem, though. This was more or less confirmed when issues vanished when I got rid of those cards.
That not everyone has issues with U59 64b client indicates that differences from installation to installation prevent the buggy behavior. That narrows it to drivers or configuration, since we're all using the same client code.
The whole finger-pointing game of which "thing" has the bug is pointless to end-users. What really matters is can DDO do something to avoid that behavior. They're the ones with upset customers. The "where" of the bug just determines how easy it is for SSG to find and deal with.
Other things about my (mostly not buggy) system using the 64b client that might be different from the buggy ones: system has most security features enabled (DEP always on for everything, hyper-v enabled, not running client in admin mode, etc etc), EAX is disabled, Run Arm sounds disabled, Sound & Voice playback use the same device, Microphone uses a different device. All devices are USB (sound & mic). DDO's displayed sound device is "OpenAL Soft". There's no "HW" choice. If you have a Soft/HW choice, perhaps try the other one.
The one sound bug my client still has is that now and then it will boot up with zero sound. On checking the Audio config, it shows no sound devices as selectable. This is odd, considering I will usually have both devices playing sound while DDO can't find a sound device. Only fix I've found is to restart the client.