After investigating the issue, the SQL from this plugin used to CREATE the wp_option_tree table upon activation, does not translate properly to TSQL via the most recent version of the wu-plugin, 'wp-db-abstraction'.
I therefore created the table myself and commented out any part of OptionTree that attempts to create or drop table.
After further testing, no queries are working with this plugin. Activation INSERTS work, but you can't update any options etc. Looks like this needs a lot of work to be database-agnostic. The SQL is tailored to MySQL only.