Error "Index was outside the bounds of the array" on launch, after problem opening Sql Editor (4311294)

The following error is displayed when launching Toad. Issue first started after trying to open SQL Editor.

System.IndexOutOfRangeException

Index was outside the bounds of the array.

 Stack Trace: at DevExpress.XtraBars.Docking2010.Views.Tabbed.TabbedView.PatchActiveChildren(Point offset) at DevExpress.XtraBars.Docking2010.DocumentManager.PatchChildrenCore() at DevExpress.XtraBars.Docking2010.DocumentManager.PatchActiveChildren() at System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme) at System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(Object obj) at System.Threading.ExecutionContext.runTryCode(Object userData) at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme) at System.Windows.Forms.Control.InvokeMarshaledCallbacks()

With Toad closed:

1. Go to C:\Users\<username>\AppData\Roaming\Quest Software
2. Rename folder 'Toad for DB2 X.x' to 'Toad for DB2 X.x_old' where X.x is the latest version of Toad.
3. Relaunch Toad
4. If it launches successfully, then go ahead and close Toad again.
5. Go back to the 'C:\Users\<username>\AppData\Roaming\Quest Software\Toad for DB2 X.x_old' folder and copy Connections.xml to the newly created 'Toad for DB2 X.x' folder.
6. Relaunch Toad