This worked for me on Plesk 11, running on CentOS.
If you're gettng a 500 error and your pages are not coming up because PHP is timing out, this is how you fix it:Edit the file:
/etc/httpd/conf.d/fcgid.conf
Specifically, change
FcgidIOTimeout 45
to
FcgidIOTimeout 3600
3600 seconds = 1 hour. Should be long enough for most but adjust upwards if required. I saw one example quoting 7200 seconds in there.
Finally, restart Apache to make the new setting active.
apachectl graceful
