This can happen if the Flash plugin has focus. You can try to click outside the Flash plugin area or in the user interface part (e.g. location bar) to set focus elsewhere.

Why can't I adjust the volume while its focused? Also, the volume still cannot be controlled if I click elsewhere on the same tab, but only if I pause the video.

I think I might be experiencing the same problem but it seems to happen randomly not mention Ive been having issues with my laptop keyboard for a while now so it might just be the keyboard itself.

For me, it's not a keyboard issue. My computer is relatively new.

LOL so is mine my Lenovo Thinkpad Edge is just a little over a year old and my problem is probably a manufacturing defect since Ive noticed issues similar to this one for over 5 months now.

Oh...yeah mine is an Edge too. But I have no problems with hardware whatsoever.

Well hopefully you don't have any issues with the keyboard like I been experiencing.

I'm using a year old Toshiba Satellite and I've also experienced this problem with Flash 11.3. I think it's a Firefox/Flash issue because 11.2 was (and is after I downgraded) working fine when I try to adjust the volume after I clicked on something using the flash plugin. Has this issue been reported as a bug yet?

Ive looked into this further and I'm having the exactly the same problem please fix this Mozilla.

Same problem except keyboard volume keys work fine, but programmable logitech mouse volume control stop working, Started after recent flash player update. Adobe said to revert back to older flash player- temporary solution. Needs to be fixed between the two big guns.

I'm able to use the latest version now by disabling the protected mode for flash. The instructions to do it are at the bottom of this page: http://forums.adobe.com/thread/1018071