Cannot access admin, but actual site us up and working fine.

My website is working fine, but all of a sudden I cannot access my admin page. I did not make any changes to the site when this error took place. The message I get when I try to access admin is:

Linux host185.hostmonster.com 2.6.28-10.40.intel.E1000E.BHsmp #1 SMP Thu May 20 14:03:42 MDT 2010 x86_64

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /home1/dreacout/public_html/admin/includes/functions/extra_functions/functions.php:2) in /home1/dreacout/public_html/includes/functions/sessions.php on line 108

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home1/dreacout/public_html/admin/includes/functions/extra_functions/functions.php:2) in /home1/dreacout/public_html/includes/functions/sessions.php on line 108

Warning: Cannot modify header information - headers already sent by (output started at /home1/dreacout/public_html/admin/includes/functions/extra_functions/functions.php:2) in /home1/dreacout/public_html/admin/includes/init_includes/init_templates.php on line 36

Warning: Cannot modify header information - headers already sent by (output started at /home1/dreacout/public_html/admin/includes/functions/extra_functions/functions.php:2) in /home1/dreacout/public_html/admin/includes/functions/general.php on line 21

I have been using zen cart for a few years now and have been able to solve most problems by reading the forum. I have not seen an error like this one, and have no clue where to start. I am running version 1.38 and was planning to update. I also contacted my hosting company to see if they made any changes that would cause this problem, they were clueless. Anyone please help!! Thanks in advance

my url is http://www.dreacustomdesigns.com

These messages are telling your that a whole series of failures are occurring for the same reason, namely that output has been sent prematurely to your browser by the beginning of your admin/includes/functions/extra_functions/functions.php file.

Sound like that file is corrupted, but only you have access to the file on your server to see what's happened to it.

Is it possible for me to reload some of the files? I was thinking of backing up my database, and just installing a fresh version of zencart. I want to make sure something like this does't happen again. So if anyone can give me any clue to as to how this happened I would appreciate it.