In order to be able to find the correct solution to your problem, we require some more non-personal information from you. Please do the following:
Click the Firefox button at the top left, then click the Help menu and select Troubleshooting Information from the submenu. If you don't have a Firefox button, click the Help menu at the top and select Troubleshooting Information from the menu.
Now, a new tab containing your troubleshooting information should open.
At the top of the page, you should see a button that says "Copy text to clipboard". Click it.
Now, go back to your forum post and click inside the reply box. Press Ctrl+V to paste all the information you copied into the forum post.