diff --git a/SourceGen/MainController.cs b/SourceGen/MainController.cs
index ce4e88e..d8f7698 100644
--- a/SourceGen/MainController.cs
+++ b/SourceGen/MainController.cs
@@ -4421,8 +4421,12 @@ namespace SourceGen {
             if (!Sgec.ImportFromFile(sgecPathName, mProject, cs, out string detailMsg)) {
                 MessageBox.Show("Failed: " + detailMsg);
             } else {
-                ApplyUndoableChanges(cs);
-                MessageBox.Show("Success: " + detailMsg);
+                if (cs.Count != 0) {
+                    ApplyUndoableChanges(cs);
+                    MessageBox.Show("Success: " + detailMsg);
+                } else {
+                    MessageBox.Show("Success; no changes were made.");
+                }
             }
         }
 
diff --git a/SourceGen/Sgec.cs b/SourceGen/Sgec.cs
index d02d053..c963456 100644
--- a/SourceGen/Sgec.cs
+++ b/SourceGen/Sgec.cs
@@ -100,10 +100,12 @@ namespace SourceGen {
             int prevOffset = -1;
             using (StreamWriter sw = new StreamWriter(pathName, false, new UTF8Encoding(false))) {
                 for (int offset = 0; offset < proj.FileDataLength; offset++) {
-                    if (!string.IsNullOrEmpty(proj.Comments[offset])) {
-                        sw.WriteLine(SET_COMMENT + " " +
+                    if (proj.Notes.TryGetValue(offset, out MultiLineComment nt)) {
+                        SerMultiLineComment serCom = new SerMultiLineComment(nt);
+                        string cereal = ser.Serialize(serCom);
+                        sw.WriteLine(SET_NOTE + " " +
                             PositionStr(offset, prevOffset, proj.AddrMap, relMode) + ':' +
-                            proj.Comments[offset]);
+                            cereal);
                         prevOffset = offset;
                         numItems++;
                     }
@@ -116,12 +118,10 @@ namespace SourceGen {
                         prevOffset = offset;
                         numItems++;
                     }
-                    if (proj.Notes.TryGetValue(offset, out MultiLineComment nt)) {
-                        SerMultiLineComment serCom = new SerMultiLineComment(nt);
-                        string cereal = ser.Serialize(serCom);
-                        sw.WriteLine(SET_NOTE + " " +
+                    if (!string.IsNullOrEmpty(proj.Comments[offset])) {
+                        sw.WriteLine(SET_COMMENT + " " +
                             PositionStr(offset, prevOffset, proj.AddrMap, relMode) + ':' +
-                            cereal);
+                            proj.Comments[offset]);
                         prevOffset = offset;
                         numItems++;
                     }
@@ -201,6 +201,14 @@ namespace SourceGen {
 
                 prevOffset = offset;
 
+                if (!proj.GetAnattrib(offset).IsStart) {
+                    // This causes problems when we try to do a LineListGen update, because
+                    // we specifically request it to do the modified offset, which happens to
+                    // be in the middle of an instruction, and it gets very confused.
+                    detailMsg = "Line " + lineNum + ": attempt to modify middle of instr/data item";
+                    return false;
+                }
+
                 string cmdStr = matches[0].Groups[GROUP_CMD].Value;
                 string valueStr = matches[0].Groups[GROUP_VALUE].Value;
                 switch (cmdStr) {