Index: FileTextLines.cpp
===================================================================
--- FileTextLines.cpp	(revision 18937)
+++ FileTextLines.cpp	(working copy)
@@ -251,6 +251,38 @@
 		return FALSE;
 	}
 
+    //check lines for internal null symbols
+    bool bFoundInternalNullSumbols = false;
+    size_t bytePos = 0;
+    LPBYTE pFileBufAsBytes = (LPBYTE)pFileBuf;
+    if ((m_UnicodeType == UTF8)||(m_UnicodeType == UTF8BOM)||(m_UnicodeType == ASCII))
+    {
+        //no nulls at all
+        for(; bytePos < dwReadBytes; bytePos++)
+        {
+            if(pFileBufAsBytes[bytePos] == 0)
+            {
+                bFoundInternalNullSumbols = true;
+            }
+        }
+    } else // unicode: no two-byte nulls at the even position
+    {
+        for(; bytePos < dwReadBytes; bytePos+=2)
+        {
+            if(pFileBufAsBytes[bytePos] == 0 && pFileBufAsBytes[bytePos+1] == 0)
+            {
+                bFoundInternalNullSumbols = true;
+            }
+        }
+    }
+    if(bFoundInternalNullSumbols)
+    {
+        //todo: i18n
+        m_sErrorString.Format(_T("The file\n%s\nis not a valid text file!\nFound null symbol at pos=%u"), 
+            (LPCTSTR)sFilePath, bytePos);
+        delete [] pFileBuf;
+        return FALSE;
+    }
 	// we may have to convert the file content
 	if ((m_UnicodeType == UTF8)||(m_UnicodeType == UTF8BOM))
 	{