Can't even save a page any more.

Topics: Troubleshooting
Jul 17, 2014 at 12:45 AM
When I try to save a page in my setup of Orchard, I get the following message:
Oops. Something went wrong ... sorry

An unhandled exception has occurred and the request was terminated. Please refresh the page. If the error persists, go back
Sequence contains more than one matching element
System.InvalidOperationException: Sequence contains more than one matching element at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) at Orchard.ContentManagement.DefaultContentManager.BuildNewVersion(ContentItem existingContentItem) in c:\Orchard\src\Orchard\ContentManagement\DefaultContentManager.cs:line 450 at Orchard.ContentManagement.DefaultContentManager.Get(Int32 id, VersionOptions options, QueryHints hints) in c:\Orchard\src\Orchard\ContentManagement\DefaultContentManager.cs:line 234 at Orchard.Core.Contents.Controllers.AdminController.EditPOST(Int32 id, String returnUrl, Action`1 conditionallyPublish) in c:\Orchard\src\Orchard.Web\Core\Contents\Controllers\AdminController.cs:line 308 at lambda_method(Closure , ControllerBase , Object[] ) at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) at System.Web.Mvc.Async.AsyncControllerActionInvoker.<BeginInvokeSynchronousActionMethod>b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<InvokeActionMethodFilterAsynchronouslyRecursive>b__3f() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass48.<InvokeActionMethodFilterAsynchronouslyRecursive>b__41() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass48.<InvokeActionMethodFilterAsynchronouslyRecursive>b__41() at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass48.<InvokeActionMethodFilterAsynchronouslyRecursive>b__41()
This happens if I open a page which worked fine previously, then simply save. Someone else may have been in and I am concerned they have installed a module which may be doing this. Is the solution obvious to anyone?