I changed to ALL in logging mode and there are no logging when doing this request, so it is very hard to know what is going wrong :(

Have not tried it myself but the have added remote debugging support to Azure websites. Perhaps that and nuget packages with source files can help you?

http://azure.microsoft.com/blog/2014/05/06/introduction-to-remote-debugging-on-azure-web-sites/

Thanks Johan, I was just going to try out the remote debugging but it might not give anything, since there is no error thrown what I can see, the page behind is picking up the error and showing a friendly version it seems like.

Absolutly will the source code help me, can you point out what class and file to look in?

It appears that we do not publish our nuget packges with source publically.

However I have heard that the latest version of Reflector comes with a handy feature that makes it possible to debug into third party code, see http://www.red-gate.com/products/dotnet-development/reflector/debugging. It is licensed but I guess you could take a trial period.

Ok.
Will try that out.

Johan, I found out what is the problem

I have Spellchecker installed in the site and after deploy to Azure, it can't find it:

System.ArgumentException: Unable to find a module by assembly 'EPiServer.TinyMCESpellChecker, Version=1.0.1.75, Culture=neutral, PublicKeyToken=null'
Parameter name: moduleAssembly
at EPiServer.Shell.Paths.ToResource(Assembly moduleAssembly, String moduleRelativeResourcePath)
at EPiServer.Shell.Paths.ToResource(Type typeInModuleAssembly, String moduleRelativeResourcePath)
at EPiServer.TinyMCESpellChecker.Helpers.ModuleHelper.ToResource(String virtualPath)
at EPiServer.TinyMCESpellChecker.SpellCheckerPlugin.GetConfigurationOptions()
at EPiServer.Editor.TinyMCE.PlugInAssembler.RegisterPlugin(TinyMCEPlugIn plugin)
at EPiServer.Editor.TinyMCE.PlugInAssembler.AddToolbarRow(IList`1 buttonNames)
at EPiServer.Editor.TinyMCE.PlugInAssembler.AddSettings(TinyMCESettings settings)
at EPiServer.Editor.TinyMCE.TinyMCEInitOptions..ctor(InitType initType, IDictionary`2 options, TinyMCESettings settings, IContent content)
at EPiServer.Cms.Shell.UI.ObjectEditing.EditorDescriptors.XhtmlStringEditorDescriptor.ModifyMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.ApplyExtendersToMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes, IEnumerable`1 metadataHandlers)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.GetMetadataForProperties(ExtendedMetadata parent, Object container, Type containerType, IMetadataProvider customProvider)
at EPiServer.Shell.ObjectEditing.ExtendedMetadata.get_Properties()
at EPiServer.Cms.Shell.UI.ObjectEditing.SettingsPanelMetadataExtender.ModifyMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.ApplyExtendersToMetadata(ExtendedMetadata metadata, IEnumerable`1 attributes, IEnumerable`1 metadataHandlers)
at EPiServer.Shell.ObjectEditing.ExtensibleMetadataProvider.CreateMetadata(IEnumerable`1 attributes, Type containerType, Func`1 modelAccess

This is in the AppData-folders modules and modulesrepro, maby I have to upload them manually with ftp

The page was logging, my site was just not doing the logging, now it logs all as error

Solved it.
It was spellchecker that was not properly installed after converting to Windows Azure.

I solved it by removing spellchecker from the site

Good to know is that addon can be a problem in Windows Azure