For some unknown reason I have started to get a parse error on posts (not on home, category or pages). It reads:

Parse error: syntax error, unexpected T_STRING in /mounted-storage/home122a/sub006/sc31987-ZWIA/photodharma.net/Blog/wp-content/themes/atahualpa/functions.php(515) : eval()'d code on line 2

This is the code at that point, but it looks OK to me.

if ( strpos($center_content,'<?php ') !== FALSE ) {
ob_start();
eval('?>'.$center_content);
$center_content = ob_get_contents();
ob_end_clean();
}

I did recently install some new plugins, but I have tried disabling them with no better result.

Does anyone have any ideas what may be going wrong?

Did you change any of the code in 'The LOOP' option?

No I didn't change any code, but I cannot guarantee that some plugin or other didn't change something. However as I mentioned I disabled all recent plugins and still I have the problem.

OK, it seems to have been a problem in the Permalinks structure or maybe in the htaccess. I updated both very carefully and the pages are loading OK now.