When I use native method VixDiskLib_Write in my C# App I get VIX_E_FAIL error, if connection suddenly disappear. Is there any way to get more specified problem reason?
You can try to look into VixDiskLib log files. Default location is %TEMP%\vmware-\vix-.log location, if you didn't specify your own log function.
And you may also find something useful in server-side log files (like var\log\vmware\host.log).