permalinks cause error on pages

I use WordPress 1.5. under “options” “permalinks” I’ve entered the default permalink structure. It seems to work fine for my posts. However when I click on a page from my “pages” list, the index of my pages in the sidebar disappears. I have to go back to the main page to see my index of pages again.

Not sure if this is a permalink problem or something amiss in my theme. Any help would be appreciated. You can see my site here: http://www.shws.net/journal – thank you.