We have developed a module which enters Windows Scheduled tasks in on our server that are calling KeepAlive pages on different servers. Normally everything went fine, but since 21-07-2011 on 17:00 all our KeepAlive pages generate errors. Those errors are because on IIS level the defaultLanguage of the different websites that run there are set to VB instead of c#. Has there be any update or whatsoever that can mess up a setting like this? How can it be that suddenly the standard language on IIS level has been changed to VB instead of C#? Hope anyone has a bright idea on this issue. I'm guessing perhaps some update has been run (our machine installs updates automatically). Can anyone track this? Thanks in advance!
The default defaultLanguage is set at the IIS root level (ASP.NET -> .NET Compliation) and inherited by all websites unless redefined there.
In your scenario there seem to be two possible causes:
1) The defaultLanguage was changed at the IIS root level. Since VB is the preset defaultLangauge it would mean that your defaultLanguage was set to C# at the root level (and changed at/around the date you mentioned). It would be relatively easy to reproduce an update reverting your selected defaultLanguage C# back to VB.
2) All your sites did override the unchanged defaultLanguage set at IIS root in their own web.config and this configuration was modified in every web.config.
You could investigate if there are differences between websites inheriting defaultLanguage and websites overriding it via web.config-