Diễn đàn hỗ trợ Firefox

I have been using Firefox for awhile now and something weird is happening. I can't close tabs by clicking on the 'x' on the tab. I also can't use the back arrow and the refresh button. I can right click and close tabs that way and the bookmark bar works. The problem seems confined to the top two bars. Thank you.

Hello! I've been observing strange behaviour during the startup of a new profile window in Firefox. Before launching there is a split second pop-up with no name and flickering colours. Any idea what that might be? I installed firefox on a different win 10 pc and the same happens there