This thread on the Firefox support forum's is by someone with a similar problem, and mentions needing to potentially restart your computer after disabling color management in Firefox to get it to stick. I also tested (on Windows7 64-bit in case it makes a difference) Firefox and Chrome using this link and it says that Chrome does not support ICC profiles while Firefox supports ICC v2 profiles, have you checked that your color management is setup correctly in Photoshop? If you were editing JPEGs that were already in sRGB and told Photoshop to convert to sRGB (rather than assign an sRGB profile) that double-handling could be a cause of the problem.

I also seem to recall reading a Facebook engineering blog post about having created a minimal sRGB ICC profile that could be automatically applied to images, but Google can't find it now.

EDIT: Here is the Facebook engineering blog post describing the profile that is added to all images

UPDATE: It looks like the problem is that the images were taken using Adobe RGB rather than sRGB since manually assigning the Adobe RGB (1998) profile to both of them in Photoshop has got the color to match for me. The desaturated look in the second image is a common sign that the image was originally recorded in a wider gamut color space than the one it is currently being displayed in.