try to select the allow button with TAB and SPACE
Tab and space didn't work.
it recalls me the same behavior long time ago but for cam/mic.What I did if I recall well is to empty the cache (included persistent cache) in your browser, then uninstall completely Flash, reboot and reainstall Flash
Yeah, this is the anti-clickjacking logic kicking in. We do a check to see that the dialog isn't obscured. When stuff (like video) is moving around on the edges of the dialog, sometimes that creates a false positive and we won't take the click.
The best way to solve this is to use the storage settings in the native control panel to suppress this dialog.
Just go to Control Panel > Flash > Storage and either set Allow sites to save information to this computer, or add the host in that dialog to the whitelist by clicking on Local Storage Settings by Site