The post template is the most commonly used gadget (found in virtually every blog) - but it's not the only gadget.
Sometimes the code in one gadget may cause a problem with the other gadgets - even with the comments / posts, or the post template.
If resetting the post template doesn't solve the problem, we generally have "widget template corruption". The solution for widget template corruption is to reset the widget templates.
- First and always, backup the template.
- Go to Template - "Edit HTML", and click on the button "Revert widget templates to default".
- If the problem is severe, select "Select all widgets", otherwise select just the specific widget that is a known problem.
- Hit "Revert selected widgets".
- Hit "Save template".
- Clear cache, and restart the browser.
- If any problems or unacceptable changes in the gadgets is observed, reload the template from the backup just taken.
- If the reset solves the problem, backup the template, again.
As an alternative solution, you may be able to reset settings in the template HTML code.