I just got Win10 Pro, and the only VSTi that is giving me heartache is ARIA Player/sforzando. Garritan's site notes that the player needs to be updated (it is), but at times fails to load. What I did not learn until last night is that when either fails to load, that it is creating a .log file (for whichever program) that continues to grow in size (I must kill these apps or they will continue to build these files). For me, I found 40+ GB of .log files (yes, these are just text files!), in my C:\Users\[username]\AppData\Roaming\Garritan\ARIA Player and my C:\Users\[username]\AppData\Roaming\Plogue Art et Technologie, Inc\sforzando... talk about a massive "WTF moment"...
 
So far, I have re-installed them, using default directories (both want to use C:\Program Files (x86)\Steinberg\VstPlugins for the 32-bit versions even though I initially loaded them elsewhere) for the installers in this order (these are the current versions at the time of this post):
WIN_sforzando_v1.933.exe (from sforzando)
ARIA_1.9.3.3_Update.exe (from Garritan)
WIN_ARIA_Player_v1.872.exe (from Garritan)
 
This seems to have helped, but is still not consistent. It seems that opening the 32-bit version first alleviates the failure, but that is not 100% either (the first failure in the log is with its bit bridge on the x64 versions). That piece makes it seem that the configuration file may be playing into it somewhere, but not tracked those down yet.
 
I have also opened them all and configured them to my Saffire (versus the Realtek), since another issue may be that the sample rates mismatch and Win10 controls the Realtek). So far that seems to have helped, but even then is not 100%.
 
I wanted to share this with folks to 1) see if there is an actual "solution" to this (Garritan's site simply says to load the newest versions, which doesn't solve it) and 2) let folks know about the MASSIVE log file issue (I didn't think anything of this, and found it using the TreeSize application as I was making directory junctions to get samples off my C: drive).
 
Oddly enough, when a real host (DAW) uses these, I get no issues. This has only occurred in standalone mode (and usually the x64 versions).

That is odd.  I have sforzando x64 installed on Win 10, and have never seen anything like that!
 
I only see a bunch of small text files in 'C:\Users\[username]\AppData\Roaming\Plogue Art et Technologie, Inc\sforzando'.  Usually just one small log file per use.
 
How many log files are you getting per 'launch'?  Have you opened one in a text editor to see what it contains?
 
 

I am not at the computer ATM, but it seems the log is common, and usually small (300KB or less). One log file per launch seems to be created, and when it fails it pegs one thread (so for me is 8% which doesn't create suspicion) but also goes to 100% disk usage and adds roughly 25MB/sec to the log file. I let it go for a while thinking it would end, and that one was 5+GB. Most were roughly 200MB, so most programs do not appreciate opening them.

I didn't get too deep into the ones I opened and deleted them all, but will take a look later on. The first failure in one was the bit bridge, but the x64 version fails too. That much "plain text" is a truckload of text, so reading it all would take forever. It may be simpler to compare a proper launch log to the smallest failure I can make.

I did notice a few older Garritan threads similar, but one that stuck out more was on MS' site. A 300GB log file was created there with "ARIA" in the title, but they attributed it to a server function and had marked it solved. Apparently that was done on a work computer :)

Notepad++ is my editor of choice for text files, especially large ones.  It has a great search function that can quickly locate all lines in the file containing a specified search phrase.  https://notepad-plus-plus.org/
 
My guess would be that some error is occurring that is generating excess output to the log file, such as a loop or recursion gone awry.

Excellent, thank you. When I get some free time I will see if I can get a "controlled crash" so I can take a look at it. I am assuming it is looping, just need to get one iteration out of the file.

Well... this is odd... the log file as it runs down through checking the audio it is hitting an error on WASAPI 2...
 
In the GOOD log, it looks like this:
I:0x 610:2164:119561:WASAPI:2| name[Saffire Audio (Saffire Audio)]
I:0x 610:2164:119561:WASAPI:2| form-factor[4]
I:0x 310:2164:119577:WASAPI:2| def.SR[44100] max.CH[2] latency{hi[0.010000] lo[0.003000]}
I:0x 310:2164:119577:WASAPI: initialized ok
I:0x 310:2164:119577:after paHostApiInitializers[3].
I:0x 310:2164:119577:Passed Pa_Initialize()
I:0x 310:2164:119577:Now enumerating Audio Devices...
I:0x 310:2164:119577:Passed Pa_CountDevices()
I:0x 310:2164:119577:Found 14 :
[then checks them all]
 
In the BAD log (I got it at 79MB, woot), it looks like this (highlighted the important points):
I:0x 810:9336:91868421:WASAPI:2| name[Saffire Audio (Saffire Audio)]
I:0x 810:9336:91868421:WASAPI:2| form-factor[4]
I:0x 810:9336:91868421:WASAPI: failed PaWasapi_Initialize error[-9986|Internal PortAudio error]
I:0x 810:9336:91868421:TerminateHostApis in
I:0x 810:9336:91868421:TerminateHostApis out
E:0x 810:9336:91868421:Pa_Initialize Error number: -9986 Error message: Internal PortAudio error
I:0x 810:9336:91868421:Passed Pa_Initialize()
I:0x 810:9336:91868421:Now enumerating Audio Devices...
I:0x 810:9336:91868421:Passed Pa_CountDevices()
I:0x 810:9336:91868421:Found 4294957296 :
I:0x 810:9336:91868421:-------------------------------------------------------------------------------
E:0x 810:9336:91868421:Dev:0 pointer is null! skipping device
I:0x 810:9336:91868421:-------------------------------------------------------------------------------
E:0x 810:9336:91868421:Dev:1 pointer is null! skipping device
(etc.)
[then tries to check them all (thankfully I stopped it just shy of half a million!)]
 
Not sure why an error should throw a number that big, but I will email both Garritan and Plogue on this one. I can include Focusrite, but the software it not theirs (although the error might be).
 
Quick Edit: I shot an email to Garritan and an info copy to Focusrite.