I ran into this same problem a couple years ago though can't remember the solution =(
Here's the symptoms:
Working with a file from a different machine; the author says he created it with "default RGB" color profile.
I open in PS 7 on Mac, things look fine. I slice it up and save; the resulting images are a mix of gif and jpeg. The images look sort of OK, though when I plug the hex code into the web style sheet, it's *a lot* darker than the image in photoshop.
I've messed with color profiles a bit, switching between sRGB IEC61966-2.1, Generic RGB Profile, sRGB Profile, and No Color Management. None of them fixes the issue. Likewise converting the image file across color profiles doesn't solve it. Switching profiles around on the app and document can get the gif and jpeg output closer, though still noticibly quite different.
I also recall that the last time this happened, there was a specific order to the steps that finally fixed the problem, and I found this solution only after searching around on boards for a couple of days. Hoping that someone here can help me out...
Let me know if there's