I'd say, see if f.lux has firefox as disabled? What I mean is, you can "disable for app" and maybe you selected firefox.

If so, try this in the daytime:
Open firefox, then reopen f.lux from the applications menu.
Then, in the right click menu for f.lux look at the "disable for app" and see if firefox is selected.

Thanks - we initially did the v30 UI with the full preferences menu appearing on click. This was the idea anyway.

But this turns out not to be as easy to do on 10.6 (!) so we rolled it back, which is why the current thing is a bit clunky.

Yeah, I did a little bit when I discovered the new forum. It was kinda fun and quite educational as well. It caused me to begin using much warmer color temperatures than I used to use when getting ready for bed and still using my computer. Like right now, it's just after 5pm, I'm getting ready for bed (I don't have a consistent day/night schedule because I can't), so I have f.lux dimmed in addition to setting it to 2700K so that it's downt to 2457K. If I press Alt+Page Down again though, then it gets too dark. Even this is a bit too dark. Or, I mean, there's too much black.

So yeah, that's why I've been saying that I want to be able to choose any color temperature at any time of the day. I'm getting ready for bed right now and I'd love to be using 1200K because my eyes have adjusted to the dimmer and warmer light, but the only way to use 1200K is by setting my clock past sunset. However, I need my clock to be accurate though because I rely on it.

Anyway, so yeah fluxometer was educational and helpful and fun!

Notice in the preferences how there are different tabs: "Daytime" "Sunset" "Bedtime". Just click those individual tabs and drag the slider to be whatever you want for the color!

A few questions: Which OS version? Are you mainly using Chrome? Do you have window transparency on?

Very strange. I am using the same vintage of machine (and have been for a while) but I've never seen what you're describing on mine. Do you have any special settings, or is there anything in particular you're doing on this machine (like a lot of videos, or an unusual web browser, that sort of thing) ?

Did it ask you to "Move to Applications?" and how did you proceed with that?

I'm curious because in this mac area, a few people have had a few issues, and I want to save some work for the f.lux team with the simple stuff.

You're welcome, have a great day. ^_^