Just to clarify, if you have 3.0-3.4 cumulative average, you are put on "academic probation" (i.e. you are in danger of getting kicked out of university but they'll let you stay to see if you can redeem yourself) for one reviewing period, which means one session I think. You are only "axed" if you have <3.0. That's according to this:
http://registrar.mcmaster.ca /calen...ent/pg124.html
As for the psych requirements, you need an CA of 6.0 and a B- in each of Psych 1X03/1XX3, which is a 7. (
http://registrar.mcmaster.ca /calen...nt/pg1631.html ). But as previously stated by sinthusized, you get a chance to switch programs every year. If you don't get into your program of choice, I would definitely recommend mirroring it in order to make future transition into the program easier.