yeah i've got it as an adjustment layer on top of the comp, and I've set it at 100 IRE (would prefer 90 but then reduce luminance just makes it look too terrible).
Have you checked it against a vectorscope?
Check it in Final Cut Pro, or download a free demo of Scopio Gigio for AE here: <http://www.metadma.com/ScopoGigio.html>
I don't suppose you are using the Avid Meridian codec, are you? It has a setting for RGB (0-255) and TV (16-235).
actually, i never have problems with footage so the capture card isn't even involved- in this case the problem arose from text created in after effects which had the shine effect applied to it. i was rendering in an avid quicktime codec, but the problem still occured when i put another adjustment layer with "key out unsafe" over the top of my other adjustment layer with "reduce luminance" applied in the original comp before i'd rendered anything. so weird.
"actually, i never have problems with footage so the capture card isn't even involved-"
If you're outputting to tape then the capture card/codec combination is involved. You need to know how it handles video. There wouldn't be any problem with the video you capture because the card/codec combination has been matched. It's only when you add elements created on your computer that you need to know how the levels and luminance values are handled. Only then can you make the right decision and apply the right settings to your footage.
If you are rendering titles over a black background you can easily get into trouble with the AVID codecs if your whites are above about 190 RGB. It's the difference between white and black that gets you into trouble. In many cases, simply putting an adjustment layer on top of your timeline and applying levels with output black set to 16 and output white set to 235 will fix most titles. If there's a lot of contrast in your titles you may have to go farther.