Pop Up Pro Errors - no such file or directory

I am trying to install pop-up pro on http://studiodancecentre.com/ but whenever I activate it, I get the following errors:

open(/home/content/37/4925037/tmp/sess_25hsem0me0t1194ugd9lubpbp7, O_RDWR) failed: No such file or directory (2) in /home/content/37/4925037/html/wp-content/plugins/popover/inc/external/wpmu-lib/inc/class-thelib.php on line 114

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/content/37/4925037/html/wp-content/plugins/popover/inc/external/wpmu-lib/inc/class-thelib.php:114) in /home/content/37/4925037/html/wp-content/plugins/popover/inc/external/wpmu-lib/inc/class-thelib.php on line 114

I tried deactivating all other plugins, but the errors persisted. I deactivated it for now, but would really love to be able to use it!