This bug does not happen in Arbortext Editor 5.2, but it does happen in version 5.3: If you place the cursor near the start of a paragraph, before any text entity, then pressing Enter invokes the Quick Tags menu. If you place the cursor after the first text entity in the paragraph (assuming there is one), then pressing Enter results in the following error message in the status bar: "Cannot insert tags at cursor, because the region is protected or read-only."