Weird code when I try to post

I am running the Magazines Basic theme on my site http://www.victoriavisits.co.uk and when I try to preview a post I am getting the following message:

Warning: mt_rand(): max(-727379969) is smaller than min(1215752192) in /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-content/plugins/mojo-marketplace-wp-plugin/inc/user-experience-tracking.php on line 60 Warning: mt_rand(): max(-727379969) is smaller than min(1215752192) in /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-content/plugins/mojo-marketplace-wp-plugin/inc/user-experience-tracking.php on line 60 Warning: mt_rand(): max(-727379969) is smaller than min(1215752192) in /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-content/plugins/mojo-marketplace-wp-plugin/inc/user-experience-tracking.php on line 60 Warning: mt_rand(): max(-727379969) is smaller than min(1215752192) in /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-content/plugins/mojo-marketplace-wp-plugin/inc/user-experience-tracking.php on line 60 Warning: mt_rand(): max(-727379969) is smaller than min(1215752192) in /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-content/plugins/mojo-marketplace-wp-plugin/inc/user-experience-tracking.php on line 60 Warning: Cannot modify header information – headers already sent by (output started at /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-content/plugins/mojo-marketplace-wp-plugin/inc/user-experience-tracking.php:60) in /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-admin/post.php on line 233 Warning: Cannot modify header information – headers already sent by (output started at /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-content/plugins/mojo-marketplace-wp-plugin/inc/user-experience-tracking.php:60) in /hermes/waloraweb030/b72/moo.vevivoscom/VictoriaVisits/wp-includes/pluggable.php on line 1173

Please could someone help with what the problem is?
Thanks!