500 error when activating Marketpress

Hey guys, I'm getting a 500 error when installing Marketpress. Here are my debug reports:

Notice: Undefined index: allowed in /home4/urbanruc/public_html/wp-content/plugins/marketpress/marketpress.php on line 505

Notice: Undefined index: page in /home4/urbanruc/public_html/wp-content/themes/DynamiX/lib/adm/index.php on line 1914

Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 232 bytes) in /home4/urbanruc/public_html/wp-admin/includes/list-table.php on line 104

I am using the Dynamix theme, which has caused errors before (see: https://premium.wpmudev.org/forums/topic/500-error-when-fundraiser-is-activated#post-200924)

So I changed back to Twenty Eleven and tried activating Marketpress and was presented with this error:

Notice: Undefined index: allowed in /home4/urbanruc/public_html/wp-content/plugins/marketpress/marketpress.php on line 505

I'm looking into the line's mentioned in the errors, any ideas on your end?