Just wondering if anyone has heard of a solution to this problem.
Had voice chat working fine on UT2K4 from the get go. I'd press the key (F) and see the green bars on the side of the screen. Could order around bots just fine and online was fine too, no problems at all
Then after not playing it for a while, I booted it up one day and voice chat wasn't working anymore. I'd press F, the sound would get quiet, but no green bars would appear at all on the side of the screen, bots didn't respond to anything and no one could hear me online. Mic works fine in Windows (tested in sound recorder, Audacity and teamspeak) and games like Team Fortress 2. Just not in UT2K4.
Tried on another compy (fresh windows install) and the same problem. I tried to think what was in common with the two machines, and realised I'd installed a Logitech USB headset on both recently, which installs its own audio drivers that the compy switches to when the headset is plugged in (otherwise I use Realtek onboad audio). Tried the USB headset as well, but no dice. Only other programs I've installed have been other games for the most part.
Have tried changing audio modes (safe mode, 3d audio, ect), turning on/off the use openal system driver toggle, updating openal drivers, turning on and off voice chat, changing levels, keybindings and a whole bunch of other things. My UT install is fresh and I haven't added any content or mucked around with .ini settings.
I've heard voice chat not working is a problem a lot of people have had with no solution and that Epic apparently couldn't replicate the problem, so I was just wondering if anyone here had any thoughts on the subject.
Online it's not so bad (use Vent or TS), but I miss being able to order bots around in single player/instant action with my voice. Onslaught just isn't what it used to be, once you get used to voice chat, it's hard to go back.

Uninstall the drivers for the USB headset, then try.
If that doesn't work, uninstall the correct drivers for the microphone you're using / general sounddrivers, then reinstall the same drivers.
If that doesn't work, tell me what sound configuration you have on your computer (external / internal sound card, what PCI slot is the card plugged into, what card is it, what can you recall that you've done except the USB headset-thing).
You could also try to check the game settings and verify that something there hasn't been mysteriously set to something wrong.

Uninstalled the USB headset and uninstalled/reinstalled latest sound drivers(Realtek HD Sound Drivers). Checked all settings, tried again and it didn't work (went quiet but no green bars, both in single and multiplayer). Checked mic in sound recorder again and works fine there.
Running on a Toshiba Laptop (Vista), using integrated (AC97) sound with Realtek HD Audio drivers. Heaset is plugged into 3.5mm stereo output and microphone jacks. The other compy I tested on was a custom built one running XP, also using onboard AC97 audio and I'd installed that USB headset on there too (that's the one I use it on now)
To my memory, installing that Logitech USB headset is the only real change I'd made to my compy (don't use it on my lappy anymore). Only other changes have been installs/uninstalls of other games.
Took a little while to test these, been a little busy lately.

I noticed I had this problem too. I'll also look into it for you as well and report back if I get anywhere.

Sorry for the long update, but I also cannot find anything on how to fix this. I've checked numerous forums and sites, and still can't find anything. Tweaking all my mic and game settings also didn't work for me. If I do find a fix, I'll post it here.