This is how it works in my case:
o- Left-Click on Alerts
o- the screen darkens, the popup window shows the alerts
o- Left-Click on Delete All
o- The dialogue window shows "Remove alerts? This can not be undone."
o- Click "Yes", that returns you to the forum
o- If you click "Alerts" again, the window shows no Alerts.
o- Left-Click on Alerts
o- the screen darkens, the popup window shows the alerts
o- Left-Click on Delete All
o- The dialogue window shows "Remove alerts? This can not be undone."
o- Click "Yes", that returns you to the forum
o- If you click "Alerts" again, the window shows no Alerts.