View source for Requested URL was not found on this server

My version 5.4.3 site no longer can find any pages other than the home page. In fact when I try to log in or look at any page, I get a //was not found on this server// message.

This problem occurred immediately after I logged in with admin.php and attempted to change the Timezone which is found under Preferences | System. Unfortunately I had not backed the system up prior to making this change AND I had not taken the system offline prior to making the change. Does anyone have suggestions how I can make the site operational again? I have examined the config file and noted that it had not changed (date didn't change) as a result of making this change. Is there something I can change in the MySQL database to make this work again?

My server does not support mod-rewrite even though there still is a check in the last entry on the System page (Use mod_rewrite).

The only thing that I can do is add **?page=HomePage/edit** to the url and get the edit side of the page. I did that when I was logged in as administrator but now that I have closed my browser, I cannot get to the Login page or any page.