I am pretty sure your problem with CS5 "Photoshop manages colors" is not specific to the driver (if Main/Color Mode is grayout and defaults to "Color" then yes it is), CS5 or 10.6.5 but specific to your computer. Let us know what you find with your iPF5000.
Hi Doyle, Eric, et al.,
Ok, so today I ran the same CS5/OS10.6 "photoshop manages colors" trial on my iPF5000, Epson 3880, and iPF8100. Conclusion. I get color managed output (print matches PS softproof) with the ipf5000 and the Ep3880, but 8100 is no good. As I noted previously, no color adjust is set correctly, but the printed result looks like either the source profile or the printer profile is being switched with something like an sRGB profile which causes the whole print to look dull. Yet I get good output from ID to the 8100 using ID's "let Indesign manage colors" workflow, so there's also something specific to PSCS5 or old versus new Apple API's going on here.
Hence, I have to conclude mainly that I have an 8100 driver bug, but one that only seems to waken when printing from PSCS5. ID is thus my workaround until I can figure something else out or Canon updates the driver (like Canon just did for the x300 series printers). Weird that the even older x000 series printers don't have the same problem.
Thanks Eric for the suggestion to my other Canon. I probably would have gotten there eventually, but there are so many possible combinations of print settings to try that it could have taken me days!