pgAgent and postgreSQL problem

Folks, I am hoping for some help as I'm a newbie to this.

I downloaded the postgreSQL software for my mac as I am planning to
learn SQL and database use on the web for various uses. (have used
access in the past, but multiple user access is a problem!)

Used stackbuilder to load the program and also the add on "pgAgent"
as I thought it would eventually be useful. All seemed to load up
last night and I then folded the lid of my macbook pro (late 2008,
intel duo 2.4, mountain lion).

I have lifted the lid of the laptop today and am faced with my
account picture as usual but with my account name changed to
"pgAgent" and an additional account called "PostgreSQL", both of
which are password protected! (I am used to putting my usual password
in after putting the laptop to sleep or after the screen saver kicks
in)

I have tried every conceivable password that I know without any
success!!!

Is there a default password that pgAgent uses?

How can I get into my computer again?

hopefully yours!

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