Error message 2.0.3.1

When I get to the install stage, the Public Licence box appears and the Continue button too, but the error message below also pops up.

I tried simply clicking the Continue button to see what happens, but all that occurs is that I'm taken to a blank page where a repeat of the error message below shows its face.

Anyone any ideas how I can move beyond this impasse?

Warning: session_start() [function.session-start]: open(/tmp/sess_d10788478eecb97d1d35385b539a1815, O_RDWR) failed: Permission denied (13) in /home/lorrab/public_html/system/library/session.php on line 12

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/lorrab/public_html/system/library/session.php:12) in /home/lorrab/public_html/system/library/session.php on line 12

Warning: Unknown: open(/tmp/sess_d10788478eecb97d1d35385b539a1815, 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 () in Unknown on line 0

The /tmp folder is not writable. You should contact your hosting support.

Thanks for the heads up, really appreciated.