IIS I/O operation error (Status 500)

I have web server running on Windows Server 2008 R2 SP1. There is IIS 7.5

I deployed API on this server. It's working fine in all browsers, but when I try to call it from mobile application every time i recieve timeout error. For API calls I use https and on server installed valid certificate.

I switched on failed request tracing and there was following error:

ModuleName    IIS Web Core    
Notification    1     
HttpStatus    500     
HttpReason    Internal Server Error     
HttpSubStatus    0     
ErrorCode    2147943395     
ConfigExceptionInfo         
Notification    BEGIN_REQUEST 
ErrorCode    The I/O operation has been aborted because of either a thread exit or an application request. (0x800703e3) 

Does anyone know what can cause this? I'm 100% sure that mobile app requests are correct. I believe there is something wrong with server.

This is most probably a certificate issue or Windows 2008 R2 Bug.