Fatal Error in opening comments

The error messages:

Warning: main(../../../wp-blog-header.php): failed to open stream: No such file or directory in /home/leewind/public_html/blogs/wp-content/themes/bluehorizon/comments-popup.php on line 4

Warning: main(../../../wp-blog-header.php): failed to open stream: No such file or directory in /home/leewind/public_html/blogs/wp-content/themes/bluehorizon/comments-popup.php on line 4

Warning: main(../../../wp-blog-header.php): failed to open stream: No such file or directory in /home/leewind/public_html/blogs/wp-content/themes/bluehorizon/comments-popup.php on line 4

Fatal error: main(): Failed opening required ‘../../../wp-blog-header.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/leewind/public_html/blogs/wp-content/themes/bluehorizon/comments-popup.php on line 4

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Could someone please help me where I should start to fix this problem? I didn’t realize this problem until recently. I think it must have been there after I tried unsuccesfully upgrading WP to version 2.0.4 (I’ve even being denied to the blog main page before but it was ok again after editing some lines with my webhoster’s file editor.)

Any help would be greatly appreciated! Thanks millions.