Help with Fatal Errors

Haven’t been looking at the site for a few hours, went to add a couple of links on pages and suddenly the errors I used to get sporadically are happening on almost every click.

Most common:

Fatal error: Out of memory (allocated 60817408) (tried to allocate 52 bytes) in /home/sitename/public_html/wp-includes/plugin.php on line 164

Next most common:

Fatal error: Out of memory (allocated 60817408) (tried to allocate 14965 bytes) in /home/sitename/public_html/wp-includes/functions.php on line 251

This shows up — only on the home page (which is a static page) — right under the header:

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/sitename/public_html/wp-content/themes/thesis_182/lib/html/frameworks.php:6) in /home/sitename/public_html/wp-content/plugins/pro-sites/pro-sites.php on line 639