I don't think this just happens with 5.1 because for months now I have seen the following error inside the striking folder in the error_log file:
[08-Feb-2012 23:02:53] PHP Fatal error: Call to undefined function get_header() in /home/webuser/public_html/wp-content/themes/striking/index.php on line 1
^ I think the above error may be created when a spammer tries to call a page/comment file the wrong way, this is just a guess though.
Here are a few new errors in the root public_html error_log: [23-Feb-2012 03:49:42] PHP Warning: imagecreatetruecolor(): Invalid image dimensions in /home/webuser/public_html/wp-includes/media.php on line 1010 [23-Feb-2012 03:49:42] PHP Warning: imagecopyresampled() expects parameter 1 to be resource, boolean given in /home/webuser/public_html/wp-content/themes/striking/framework/functions/common.php on line 281 [23-Feb-2012 03:49:42] PHP Warning: imagejpeg() expects parameter 1 to be resource, boolean given in /home/webuser/public_html/wp-content/themes/striking/framework/functions/common.php on line 310
These are new ones also in the root public_html error_log, but I have seen reports of these on the latest version on this forum: [23-Feb-2012 04:15:30] PHP Warning: Division by zero in /home/webuser/public_html/wp-content/themes/striking/framework/helpers/themeGenerator.php on line 396 [23-Feb-2012 04:15:30] PHP Warning: Division by zero in /home/webuser/public_html/wp-content/themes/striking/framework/functions/common.php on line 360
they where reported here also and as i recall turning timthumb on or off in the advanced settings of striking with the clearing of the cache (also a option/setting in the advanced section of the striking settings) solved the problem.
Thank you for the suggestion, but I have had timthumb turned off of my site since the option was available a few versions back, and I have cleared the cache several times. I did note a problem with using child sites from Striking with the cache in another thread of mine.