We're currently experiencing an error when using the 'Create new link' on LinkItemCollection and via richtext editor.

Any ideas? We're on EPiServer 7.9.1.0 and we upgraded from 7.1

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It's attempting to access: http://XXX/episerver/shell/Stores/metadata/episerver.cms.shell.ui.objectediting.internalmetadata.linkmodel?dojo.preventCache=1405607140987

Returning the following snippet of the error log:

[NotImplementedException: The method or operation is not implemented.]
   System.Web.HttpContextBase.GetGlobalResourceObject(String classKey, String resourceKey, CultureInfo culture) +29
   System.Web.Mvc.ClientDataTypeModelValidatorProvider.GetUserResourceString(ControllerContext controllerContext, String resourceName) +159
   System.Web.Mvc.ClientDataTypeModelValidatorProvider.GetFieldMustBeNumericResource(ControllerContext controllerContext) +15
   System.Web.Mvc.d__0.MoveNext() +221
   System.Linq.d__14`2.MoveNext() +293
   System.Linq.d__14`2.MoveNext() +397
   System.Linq.d__aa`1.MoveNext() +86
   System.Linq.Enumerable.FirstOrDefault(IEnumerable`1 source) +164
   EPiServer.Shell.ObjectEditing.ExtendedMetadata.GetClientValidatorRule() +183
   EPiServer.Shell.ObjectEditing.ExtendedMetadata.GetInvalidMessage(LocalizationService localizationService) +72
   EPiServer.Shell.ObjectEditing.ExtendedMetadata.GetEditorSettings(LocalizationService localizationService) +281
   EPiServer.Shell.UI.Rest.DefaultMetadataStoreModelCreator.CreateFromModelMetadata(ExtendedMetadata metadata, LocalizationService localizationService, UIDescriptorRegistry uiDescriptorRegistry, ISelectionFactory[] selectionFactories, Boolean alwaysCreateChildProperties) +912
   EPiServer.Shell.UI.Rest.DefaultMetadataStoreModelCreator.ExtractMetadataFromProperties(ExtendedMetadata metadata, MetadataStoreModel MetadataStoreModel, LocalizationService localizationService, UIDescriptorRegistry uiDescriptorRegistry, ISelectionFactory[] selectionFactories) +212
   EPiServer.Shell.UI.Rest.DefaultMetadataStoreModelCreator.CreateFromModelMetadata(ExtendedMetadata metadata, LocalizationService localizationService, UIDescriptorRegistry uiDescriptorRegistry, ISelectionFactory[] selectionFactories, Boolean alwaysCreateChildProperties) +1285
   EPiServer.Shell.UI.Rest.DefaultMetadataStoreModelCreator.Create(ModelMetadata metadata) +36
   EPiServer.Shell.UI.Rest.MetadataStore.Get(String id, String modelAccessor) +327