I am trying to upgrade from 7.0.4 to 7.1.4 and am getting the following error which occurs during the upgrade from within the browser:

Sequence contains more than one element.

Here is the error in the log file:

2014-08-05 10:07:59,567 [33] ERROR Umbraco.Web.Install.Controllers.InstallApiController - [Thread 34] Installation step DatabaseUpgrade failed.
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidOperationException: Sequence contains more than one element
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
   at Umbraco.Core.Configuration.GlobalSettings.RemoveSetting(String key)
   at Umbraco.Web.Install.InstallSteps.DatabaseUpgradeStep.Execute(Object model)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Umbraco.Web.Install.Controllers.InstallApiController.ExecuteStep(InstallSetupStep step, JToken instruction)
   at Umbraco.Web.Install.Controllers.InstallApiController.PostPerformInstall(InstallInstructions installModel)
2014-08-05 10:07:59,567 [33] INFO  Umbraco.Web.Install.Controllers.InstallApiController - [Thread 34] Step completed (took 53ms)
2014-08-05 10:07:59,567 [33] ERROR Umbraco.Web.Install.Controllers.InstallApiController - [Thread 34] An error occurred during installation step DatabaseUpgrade
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidOperationException: Sequence contains more than one element
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
   at Umbraco.Core.Configuration.GlobalSettings.RemoveSetting(String key)
   at Umbraco.Web.Install.InstallSteps.DatabaseUpgradeStep.Execute(Object model)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Umbraco.Web.Install.Controllers.InstallApiController.ExecuteStep(InstallSetupStep step, JToken instruction)
   at Umbraco.Web.Install.Controllers.InstallApiController.PostPerformInstall(InstallInstructions installModel)