Thanks for the reply moshu! I appreciate the help!
The blog was a MovableType about a year ago and I've been with WP for all that time and have done numerous updates since.
The problem started when I was on 2.0 and I was playing around with different Themes I had uploaded. All I was doing was clicking on a theme, taking a look at it and then going on to the next theme to see what it looked like when it happened. I wasn't even tinkering around with any of the theme's pages when it happened. I went up to 2.2 to see if it got solved, but it persists. Even if I go back to the theme I've been using for the past 6 months it's jacked up - the white of the page background stops at the header. And I didn't change any of the content on the theme pages - which makes me crazy trying to figure out what suddenly went wrong?!
So, I had this problem before creating the WP Page "Archives.php" - my Archives directory was showing up as it is now in a list directory with no theme. I made the Archives.php page out of the instructions of the current theme I'm using.... see those instructions here (the theme I'm using is by the same author and he used the same Archives tab at the top of my current theme too):
Thanks for any help... I'm totally lost as to why this suddenly happened.