Weird Exception while initOnce

[Evengard]

After several days running fine, I surprisingly got a weird exception:

Exception while initOnce: System.NullReferenceException: Object reference not set to an instance of an object
  at HyperFastCgi.AppHosts.AspNet.MonoWorkerRequest.MapPath (System.String path) [0x00036] in <4431df8bb39a4081b5f2b5304da2a6e8>:0
  at HyperFastCgi.AppHosts.AspNet.AspNetNativeWebRequest.GetFilePath () [0x00029] in <4431df8bb39a4081b5f2b5304da2a6e8>:0
  at System.Web.HttpRequest.get_FilePath () [0x0001c] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.HttpRequest.get_BaseVirtualDir () [0x0000b] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.HttpRequest.MapPath (System.String virtualPath) [0x0000d] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.Hosting.HostingEnvironment.MapPath (System.String virtualPath) [0x00042] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.Hosting.DefaultVirtualPathProvider.DirectoryExists (System.String virtualDir) [0x00016] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.Configuration.WebConfigurationManager.FindWebConfig (System.String path, System.Boolean& inAnotherApp) [0x0001f] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration (System.String path, System.String site, System.String locationSubPath, System.String server, System.String userName, System.String password, System.Boolean fweb) [0x00026] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.Configuration.WebConfigurationManager.GetSection (System.String sectionName, System.String path, System.Web.HttpContext context) [0x0000d] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.Configuration.WebConfigurationManager.GetSection (System.String sectionName, System.String path) [0x00007] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.Configuration.WebConfigurationManager.GetWebApplicationSection (System.String sectionName) [0x00033] in <d3ba84a338d241e2ab5397407351c9cd>:0
  at System.Web.HttpApplication.InitOnce (System.Boolean full_init) [0x00059] in <d3ba84a338d241e2ab5397407351c9cd>:0

What may be the cause of this? Only restarting hyperfastcgi helped, the app was throwing a 500 error with the same exception.

At the same time getting theese:

fcgi-transport.c:226: send_output():    can't find request n=819
fcgi-transport.c:226: send_output():    can't find request n=819
fcgi-transport.c:262: end_request():    can't find request n=819

And theese:

libev.c:317: cmd_error():       Remote host disconnected from fd 26.
libev.c:317: cmd_error():       Remote host disconnected from fd 23.

[xplicit]

This is mono issue, I met it sometimes when application is starting. It does not relate to HyperFastCgi, because it can appear in XSP too. The only way I know to avoid this is to restart application again.