Hi,
I’m working with Blender 2.62 on a Mac (OS 10.6) and would like to render the files on a PC (Windows 7) because it’s faster. But although I have worked with color management turned on in the Blender file the render from the PC is much too dark (looks like the render on the Mac without color management). I’m not using any nodes yet, just simple materials and lights.
Is this a platform problem?
Are you looking at the PC render on the the Mac?
Or are you judging each render on a separate monitor?
I looked at the PC render on the Mac.
I believe that you can adjust the PC’s gamma from the 1.8 to the Mac 2.2.
Or, you can just adjust your mac’s monitor gamma to 1.8 for viewing.
I’m not sure how/if the color correction is taking into account the monitor’s gamma. I’m guessing it is though.
too many variables for an accurate response.
you are probably using different color spaces without knowing it, also caring about the precise tone and about color reproduction is only a big big big waste of time, you have to care about contrast, maybe brightness, the general color tones of your image, but caring about the colors is a thing impossible to achieve at the actual state of technology.
yeesh, I have to disagree with “caring about the colors is a thing impossible to achieve at the actual state of technology.”
I spend all day getting photographing artwork for reproduction on screen and print and I can guarantee you that it is both possible to 'care" and to “achieve” good color accuracy. The gallery I work for sells $60,000 Toulouse Lautrec Original prints to collectors who’ve never seen the print except in my photo. You better believe I’ll get my ass kicked if that Burnt Orange looks like Tangerine.
as you said “good” not “exact” 
i don’t want to go in details, but it’s a problem related to the encoding and decoding process, also this process includes infinite variables such as the lights setting, the quality of the panel of the monitor, etc etc, this problem is shared across the entire world of the digital image processing.
you mention a relatively simple and good technique, that is to say making some printing tests and see what the colors looks like, but even this process can be complicated if you are working in a professional typography with the colours mix done by hand.
you are also speaking about printing, and usually when you print you have the total control of the media ( the paper ), but when comes to an image file or a file that has to be reproduced on X monitors or, in simplest terms, a setup that differs from yours, you have almost no control over the media, and, as i said, trying to achieve the same result on all the monitors is impossible.
Yes, the game is very different for Monitor Color.
I don’t need the exact same colors but I’d expect the shadowy reddish-brown inside of a box (which it is in the Mac render) still show up as the inside of a box in the PC render and not as a plain black object with now depth at all. And I don’t think it’s just a monitor issue because the same file is ok rendered on the Mac but too dark when opened and rendered on the PC (and copied back to and watched on the Mac). But thanks anyways. 
“the same file” means exactly nothing, the file that you are considering has to be decoded, in the decoding process a color space model is used, and there are several color space model, the most used are the Srgb and the Adobe RGB.
Considering what you are reporting i think that is a normal switch from an Srgb to an Adobe RGB and viceversa, whit an Adobe RGB you can usually see more shades of colors, in particular shades of hot colors such as pink and red, the Srgb is usually a more compact space colors with a less variety of shades and usually the same image can appear darker in some areas.
The monitor is only one of all the pieces that has to be considered during this process, it’ important, but also is important how your software handles your image.
That means Blender on the PC is using a different color space model for decoding than on the Mac? Does this depend on the setup of the machine it’s running on or is it something that I have to specify within Blender?
no, usually the color space is managed by your OS, so if you want to check what color space model are you using go in the settings menu of your MAC or in the control panel of Windows.
Will do on Monday (don’t have the PC at home). Thanks.