Rookie: Can't access WP admin panel

Hi all, i am very new to WordPress, so please be patient.
I know it could all have been already answered, but after a few searches, did’t find what i was looking for.

I installed locally on my computer WordPress 3.0 via the Bitnami Worpress Stack, and i am using the theme FULLSCREEN from Graph Paper Press, for my Web portfolio.

– Once WordPress was installed, i did go right away into the WP admin panel, and then activated the FULLSCREEN theme.

– So i started writing test posts and uploading images that are used as thumbnails to be clicked to access these posts (and/or a full size art sample).

– I could also go seemlessly go back and forth between the WP admin panel and my ”local site home page”, BECAUSE there was a ”EDIT” button that was available on each of my site posts.
So Everything was ok.

THE PROBLEM IS:

Once i closed my FireFox browser, (or the computer) and went back, i could log into my local site, but could no longer access the WP admin panel, because there was no more ”EDIT” button available for each posts !

(I am not aware of any other way to access the WP admin panel, by the way)

It seems that this FULLSCREEN theme is not an easy one, but i am still hoping there is a way to fix this.

Thanks very much in advance !