diff --git a/src/generic/treectlg.cpp b/src/generic/treectlg.cpp
index 79a9facb90..92610cada4 100644
--- a/src/generic/treectlg.cpp
+++ b/src/generic/treectlg.cpp
@@ -1246,9 +1246,13 @@ wxTreeItemId wxGenericTreeCtrl::InsertItem(const wxTreeItemId& parentId,
         return AddRoot(text, image, selImage, data);
     }
 
-    int index = parent->GetChildren().Index((wxGenericTreeItem*) idPrevious.m_pItem);
-    wxASSERT_MSG( index != wxNOT_FOUND,
-                  wxT("previous item in wxGenericTreeCtrl::InsertItem() is not a sibling") );
+    int index = -1;
+    if (idPrevious.IsOk())
+    {
+        index = parent->GetChildren().Index((wxGenericTreeItem*) idPrevious.m_pItem);
+        wxASSERT_MSG( index != wxNOT_FOUND,
+                      wxT("previous item in wxGenericTreeCtrl::InsertItem() is not a sibling") );
+    }
 
     return DoInsertItem(parentId, (size_t)++index, text, image, selImage, data);
 }
diff --git a/src/gtk/dcclient.cpp b/src/gtk/dcclient.cpp
index 736b8a1332..5af43d6f27 100644
--- a/src/gtk/dcclient.cpp
+++ b/src/gtk/dcclient.cpp
@@ -1594,7 +1594,9 @@ void wxWindowDC::Clear()
 
 void wxWindowDC::SetFont( const wxFont &font )
 {
-    wxCHECK_RET( font.Ok(), _T("invalid font in wxWindowDC::SetFont") );
+    // It is common practice to set the font to wxNullFont, so
+    // don't consider it to be an error
+    //    wxCHECK_RET( font.Ok(), _T("invalid font in wxWindowDC::SetFont") );
 
     m_font = font;
 #ifdef __WXGTK20__
diff --git a/src/gtk/textctrl.cpp b/src/gtk/textctrl.cpp
index bfa26d0b92..a655706aa5 100644
--- a/src/gtk/textctrl.cpp
+++ b/src/gtk/textctrl.cpp
@@ -929,14 +929,14 @@ void wxTextCtrl::Redo()
 bool wxTextCtrl::CanUndo() const
 {
     // TODO
-    wxFAIL_MSG( wxT("wxTextCtrl::CanUndo not implemented") );
+    //wxFAIL_MSG( wxT("wxTextCtrl::CanUndo not implemented") );
     return FALSE;
 }
 
 bool wxTextCtrl::CanRedo() const
 {
     // TODO
-    wxFAIL_MSG( wxT("wxTextCtrl::CanRedo not implemented") );
+    //wxFAIL_MSG( wxT("wxTextCtrl::CanRedo not implemented") );
     return FALSE;
 }
 
diff --git a/src/gtk1/dcclient.cpp b/src/gtk1/dcclient.cpp
index 736b8a1332..5af43d6f27 100644
--- a/src/gtk1/dcclient.cpp
+++ b/src/gtk1/dcclient.cpp
@@ -1594,7 +1594,9 @@ void wxWindowDC::Clear()
 
 void wxWindowDC::SetFont( const wxFont &font )
 {
-    wxCHECK_RET( font.Ok(), _T("invalid font in wxWindowDC::SetFont") );
+    // It is common practice to set the font to wxNullFont, so
+    // don't consider it to be an error
+    //    wxCHECK_RET( font.Ok(), _T("invalid font in wxWindowDC::SetFont") );
 
     m_font = font;
 #ifdef __WXGTK20__
diff --git a/src/gtk1/textctrl.cpp b/src/gtk1/textctrl.cpp
index bfa26d0b92..a655706aa5 100644
--- a/src/gtk1/textctrl.cpp
+++ b/src/gtk1/textctrl.cpp
@@ -929,14 +929,14 @@ void wxTextCtrl::Redo()
 bool wxTextCtrl::CanUndo() const
 {
     // TODO
-    wxFAIL_MSG( wxT("wxTextCtrl::CanUndo not implemented") );
+    //wxFAIL_MSG( wxT("wxTextCtrl::CanUndo not implemented") );
     return FALSE;
 }
 
 bool wxTextCtrl::CanRedo() const
 {
     // TODO
-    wxFAIL_MSG( wxT("wxTextCtrl::CanRedo not implemented") );
+    //wxFAIL_MSG( wxT("wxTextCtrl::CanRedo not implemented") );
     return FALSE;
 }