Index: common/project.cpp
===================================================================
--- common/project.cpp	(revision 219)
+++ common/project.cpp	(working copy)
@@ -371,6 +371,8 @@
 	lcPiecesLibrary* Library = lcGetPiecesLibrary();
 	Library->OpenCache();
 
+	const Piece* pFirstExistingPiece = m_pPieces;
+
 	while (count--)
 	{
 		if (fv > 0.4f)
@@ -509,6 +511,24 @@
 			}
 			else
 				pGroup->FileLoad(file);
+
+			if (bMerge)
+			{
+				// Ensure a unique group name
+
+				int max = -1;
+				String baseName;
+
+				for (Group* pExisting = m_pGroups; pExisting && (pExisting != pGroup); pExisting = pExisting->m_pNext)
+					max = lcMax(max, InstanceOfName(pExisting->m_strName, pGroup->m_strName, baseName));
+
+				if (max > -1)
+				{
+					int baseReserve = sizeof(pGroup->m_strName) - 5; // space, #, 2-digits, and terminating 0
+					for (int num = max; (num > 99); num /= 10) { baseReserve--; }
+					sprintf(pGroup->m_strName, "%s #%.2d", (const char*)(baseName.Left(baseReserve)), max+1);
+				}
+			}
 		}
 
 		for (pGroup = pLastGroup; pGroup; pGroup = pGroup->m_pNext)
@@ -533,7 +553,7 @@
 
 
 		Piece* pPiece;
-		for (pPiece = m_pPieces; pPiece; pPiece = pPiece->m_pNext)
+		for (pPiece = m_pPieces; pPiece && pPiece != pFirstExistingPiece; pPiece = pPiece->m_pNext)
 		{
 			i = LC_POINTER_TO_INT(pPiece->GetGroup());
 			pPiece->SetGroup(NULL);
@@ -9240,7 +9260,7 @@
 	{
 		if (m_OverlayActive)
 			MouseUpdateOverlays(view, x, y);
-		else
+		else
 			view->SetCursor(view->GetCursor());
 		return;
 	}
@@ -10125,3 +10145,53 @@
 		m_ActiveView->m_OverlayScale = Dist.Length() * 5.0f;
 	}
 }
+
+// Indicates if the existing string represents an instance of the candidate
+// string in the form "<basename> (#<instance>)".
+//
+// Returns:
+//	-1  if existing is not an instance of candidate.
+//	0  if existing is an instance but not numbered.
+//	>= 1  indicates the existing instance number.
+//
+int Project::InstanceOfName(const String& existingString, const String& candidateString, String& baseNameOut )
+{
+	int einst = 0;
+	String estr = existingString;
+	estr.TrimLeft();
+	estr.TrimRight();
+
+	int div = estr.ReverseFind('#');
+	if (-1 != div)
+	{
+		char* endptr;
+		einst = strtol(estr.Mid(div + 1), &endptr, 10);
+		if (!*endptr)
+		{
+			estr = estr.Left(div);
+			estr.TrimRight();
+		}
+	}
+
+	String cstr = candidateString;
+	cstr.TrimLeft();
+	cstr.TrimRight();
+
+	div = cstr.ReverseFind('#');
+	if (-1 != div)
+	{
+		char* endptr;
+		strtol(cstr.Mid(div + 1), &endptr, 10);
+		if (!*endptr)
+		{
+			cstr = cstr.Left(div);
+			cstr.TrimRight();
+		}
+	}
+
+	if (estr.CompareNoCase(cstr))
+		return -1;
+
+	baseNameOut = estr;
+	return einst;
+}
Index: common/project.h
===================================================================
--- common/project.h	(revision 214)
+++ common/project.h	(working copy)
@@ -325,6 +325,7 @@
 	void FindClosestPieceVertexInBox(View* view, lcVector3& vertex, float x1, float y1, float x2, float y2, lcArray<Object*>& Objects);
 	void SelectAndFocusNone(bool bFocusOnly);
 	void CalculateStep();
+	static int InstanceOfName(const String& existingString, const String& candidateString, String& baseNameOut );
 
 	void FindPiece(bool FindFirst, bool SearchForward);
 	lcSearchOptions mSearchOptions;