Login Issue – Error with Script

Hello, I am getting the following error when I try to log into my blog:

Parse error: syntax error, unexpected $end in /home/a8123821/public_html/wordpress/wp-admin/custom-header.php on line 270

I have had this problem for over 2 weeks now and am unsure as to what to do. I do not believe I did anything to cause this, and do not know where I would look to try fix it. I am not sure what version of WP I am using.
Thanks,
Colm Shannon