Pinta 1.3-dev-preview on Windows XP. Now I have realized that actually now there are two crashes appearing when saving file with Save As second time. So this got to be some regression from previous week.

1. Open Pinta and open new file File | New.
2. You don't need to draw anything, just use File | Save and save file e.g.: test.png and click on Save button.
3. You don't need to change anything on canvas just use File | Save As. Error appears (this error got to be a regression, because I haven't got this error previos week):
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System.InvalidOperationException: Sequence contains no matching element
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source, Func`2 predicate)
   at Pinta.Actions.SaveDocumentImplmentationAction.OnFilterChanged(Object o, NotifyArgs args) in d:\Programming\CSharp\Pinta\Pinta\Pinta\Actions\File\SaveDocumentImplementationAction.cs:line 255
   at GLib.Object.NotifyCallback(IntPtr handle, IntPtr pspec, IntPtr gch)
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4. Click on "X" in top-right to close error message.
5. From file-type selection there is empty drop-down box! In Name field type in: test2.png and click on Save button.
6. Another error pops-up:
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System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentNullException: Value cannot be null.

Parameter name: key
   at System.Collections.Generic.Dictionary`2.FindEntry(TKey key)
   at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
   at Pinta.Actions.SaveDocumentImplmentationAction.SaveFileAs(Document document) in d:\Programming\CSharp\Pinta\Pinta\Pinta\Actions\File\SaveDocumentImplementationAction.cs:line 134
   at Pinta.Actions.SaveDocumentImplmentationAction.Activated(Object sender, DocumentCancelEventArgs e) in d:\Programming\CSharp\Pinta\Pinta\Pinta\Actions\File\SaveDocumentImplementationAction.cs:line 58
   at Pinta.Core.FileActions.RaiseSaveDocument(Document document, Boolean saveAs)
   at Pinta.Core.Document.Save(Boolean saveAs)
   at Pinta.Actions.SaveDocumentAsAction.Activated(Object sender, EventArgs e) in d:\Programming\CSharp\Pinta\Pinta\Pinta\Actions\File\SaveDocumentAsAction.cs:line 48
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
   at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
  at GLib.Signal.ClosureInvokedCB(Object o, ClosureInvokedArgs args)
   at GLib.SignalClosure.Invoke(ClosureInvokedArgs args)
   at GLib.SignalClosure.MarshalCallback(IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data)
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7. Click on "X" in top-right to close error message.
8. Now you are in the end of road. You need to click "X" in top-right of the Save Image File dialog to close the image.

Work-around:
Repeat-steps from 1 to 5.
6. File-type drop-down box still empty. From this drop-down box select "PNG image" and click on Save button. OK, now file is saved.

So it looks like this bug becomes even more annoying (two crashes in a role). It is no fun to save files (Save As) in Pinta. :)