Lemon Meringue... Puddle?

It has become tradition (if doing something two years in a row makes a tradition?) of making my husband a pie on his birthday.  Last year was a blueberry pie from scratch.  I usually go the easy route of buying a pre-made shell.  Last year I did it all by hand and it was SO tasty.  This year I decided on Lemon Meringue.  My Mom can do it, so I can too... right?

FAIL.  It tasted like Lemon Meringue.  The meringue worked like meringue.  But the filling flopped, and turned to a pool on our plates.  I'm not sure where I went wrong.  The graham cracker crust?  That's my only  theory.  That the hot filling on top of  the graham crust, caused the crust to get soft and it turned into a pile of mush.  The recipe didn't call for a graham crust, but graham crusts are so tasty I couldn't resist.  I did bake the shell prior to adding the filling but?

Do you know?  Have you made a successful Lemon Meringue?  I'd like to try again if anyone has a recipe to share :)