what is your default working space in PS?

RGB (sRGB IEC61966-2.1) ??    Apple RGB?? Apple RGB (1998) ??

you can also look into GAMMA settings...   windows uses a 2,2 gamma setting and mac uses a 1.8 so colors appear darker on widows than they do on a mac. you may be running into a similar issue between programs...  

hope it's a poke in the right direction..
if not, disregard what i said ;)

scott