I know this is an old thread but I found it today when searching for a solution to the same problem when printing. I only started having this problem after moving to a new Windows 7 computer. I'd been printing on an older Window 7 computer with no issues and was befuddled. I tried many solutions listed here and on other threads yet nothing was working. More confusing is that the test print I'd done recently using a standardized test photo was perfect. I sat back and looked at all my settings in Lightroom again with a fresh eye. I'm printing on Canon Photo Paper Plus Glossy II and had selected the "<PR> 1 Photo Paper Pro II" ICC profile in my LR print settings. I switched it to "<GL><PP> 1 Photo Paper Plus GlossyGold" ICC profile instead and what do you know? Magenta cast completely disappeared. So just in case you're coming across this thread having the same problem, try changing to another ICC profile that may be more appropriate for the paper and see if that does the trick.
My issue turned out to be a failed print head. It did not matter what advice I followed on here the magenta cast was there. I also found out it is cheaper to buy a new printer from ebay than a print head.
I know that this is an old post but I have just experienced the very same problem with a Windows 10 machine, Ligthroom CC and a Canon PRO 10S. The quickest way to lose the cast is from within Lightroom to allow the printer to manage the colours. That gives a better result than relying on the ICC profile in Lightroom itself. A far better solution is to install the Canon Print Studio Pro plugin into Lightroom and Photoshop. I am delighted to say that the problem is now SOLVED.
