Greetings. Have had the X3a upgrade for a few years and found a good time to install. X2a performed almost flawlessly, machine has W7 Home Premium, Pentium i5 Quad Core @3.4Ghz, two 500GB SATA drives, 32 GB RAM, no internet or antivirus, all superfluous services disabled. 32 bit version installed in both cases because of a few legacy plugins I just won't live without. Interface is RME Multiface HDSP (original version with most current drivers). I loaded a mix from an album project I did back in 2015, instantaneous dropout. Mix latency was set to 1024ms. FWIW, when I open the ASIO panel for the RME, the slider control for the Mix latency buffers is faded out and not adjustable, have to open a separate window and select from a menu, has always behaved that way. There is also no "Wave Profiler" function apparent. The system recognizes the RME and it has been rock solid across two computers and four version of Sonar...still have S6 P installed as a backup platform and it works fine. are there any known bugs with this a version, a patch available perhaps? Crossing swords with one of those legacy plugins? Would love to hear from anyone who has had a similar experience. Will revert to X2a if need be. Thanks.

First things first...there are updates for X3. 

Thanks, I'm all for updates.

Updates didn't help. I tried tweaking every setting I could find or think of. One possibility is a Melodyne configuration menu that popped up. I know that Celemony now requires an internet connection, my machine doesn't have one. I have an older version that is authorized to the hard drive and the updates may have messed with that. I used system restore and went back to X2a, had the same dropout issues magically appear. After more tweaking attempts, I finally tried resetting the Configuration File to default settings and everything got stable again. If I decide to make another attempt at the upgrade, I'll try this fix. Otherwise, X2a lacks for nothing I need.

I can't help, but I suggest that since you have 32 GB of RAM you really should go for the 64 bit version.
The VST bridge runs 32 bit VSTs pretty well.

I have several 24 bit plugins that are too useful to lose, hence the 32 bit choice.

If you don't mind me asking.. which plug ins ?
I believe running in 32 mode you can only use a max of 4 GB of RAM so you are wasting quite a bit of RAM here.
Also Sonar uses bitbridge which allows a lot of plug ins to be run in a 64 bit atmosphere.
 
Anyway back to your issue.
I would reinstall the Soundcard driver and check your USB cables to make sure everything is good.
Also power down/power up the device again. Sometimes the soundcard can go in to a sleep mode when plugged in but not being used.
 

Chuck Jones, BLOCKFISH, Blue Compressor, TLs 2095 limiter off the top of my head. The SSL Talkback compressor may also be in this category.
 
If you didn't see my follow-up post, went back to X2a and experienced similar dropouts, eventually fixed it by clicking on "Restore Default Settings". In the Config menu. Interesting point about the 4G RAM limits in 32 bit, will research that and consider the 64 bit option. Thanks.
 
BTW, Unsure if my version of Melodyne Essential, which is authorized to the drive, will operate in 64 bit, must research that as well.