[Plugin: Event Registration] session_start error on activation

When I activate the plugin I see the following at the top of the dashboard and the front of my site:

Warning: session_start() [function.session-start]: open(/tmp/sess_93d952b0f04c64167558a0bcff65d6c1, O_RDWR) failed: Permission denied (13) in /home/xxxx/public_html/wp-content/plugins/event-registration/er_sample_page.php on line 7

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/xxxx/public_html/wp-content/plugins/event-registration/er_sample_page.php:7) in /home/xxxx/public_html/wp-content/plugins/event-registration/er_sample_page.php on line 7

And the following at the bottom of every page:

Warning: Unknown: open(/tmp/sess_93d952b0f04c64167558a0bcff65d6c1, O_RDWR) failed: Permission denied (13) in Unknown on line 0

Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0

Any suggestions?