well when trying to update SP, there is zero ajax activity… something is killing off the processes trying to do the update… the only difference between other plugins (that are listed in wordpress.org) and simple press (or other plugins not in wordpress.org) is that we have to hook into the wp updater and provide the information for our upgrade archive… we certainly have over a million updates through the updater so its working very well… that said, something is going on that killing the process…
I was suspecting the 400 errors killing process but am now doubtful its killing it.. trying to upgrade, you get that same error 3 times and after them, http headers are active… I would still suggest getting to the bottom of that…
as to Dagon Design Form Mailer, that is another plugin that is not hosted at wordpress.org… so perhaps related…
@Benny, did you ever check your server log for more info? check right after running the update and see if any errors persits… also, perhaps try adding
define(‘WP_DEBUG’, TRUE);
to your wp-config.php file and see if more errors are reported to the screen when updating… I would do this soonest for more details… it may show why the process is getting killed off…
and you did not answer the mod_security question…
As to your deactivating and switch to default wp theme, that seems to confirm the conflict I have been postulating…
I would update all your non simple press plugins to the latest… I know wp-seo just released an urgent update because of an issue with upgrading and wp 3.7… no clue if its related, but I would get the latest and greatest of everything…