magic_quotes_gpc? Session variables

Hey gang, I was having the weirdest problems when I decided to update the code for my site(written in PHP) last modified over a year ago. The code ran fine under my home development system, but on the hosting machine(1and1.com), my code would break. Horribly. I narrowed the problem to this - If I have a variable in $_SESSION(for example, 'username') and in my page, I declare a variable (for example '$username="guest"'), I've effectively accessed and overwritten the session variable. It's been over a year, but I believe this is due to magic_quotes_gpc flag being 1 or something - I checked with my host's phpinfo page and it is set to 1. My question is(before I send my host an e-mail to ask them to turn it off for my site) is, magic_quotes_gpc IS the culprit, right? I mean the whole behavior of if you declare a variable : $_SESSION['username'] = "Mark" then you can just write $username instead of $_SESSION["username"] to access the session variable is because of magic_quotes_gpc? Thanks in advance, Mk