Not getting on at you pamdas but you've got this posted in the Absolute Beginners Forum as well and you are not meant to post about the same thing in multiple forums. I suggest you tick the beginners one as resolved and stick to this one.
Regarding the slodges you have noticed I have to agree with Canon, its not a feed problem so I assume the printer is faulty. Its Epson printers I have but I have yet to have a printer that cannot print on card as long as its not too thick.
I admit the Epsons I have have to have them fed in one sheet at a time if I am using something like 300gsm but photo paper at 220gsm it happily takes them without the need for single sheet feeding, cannot recommend either of mine to you though as both are getting on a bit and are no longer available.
I'm rather surprised the SX400 will not print on card. Who told you it wouldn't?
If no one else replies I would drop Epson an email and see what they say. My Epsons print on card ok.