I hesitated a bit about posting this as a bug because the issue should probably be resolved in the i18n modules (I also posted a comment on an issue in that module). Essentially, the issues boils down to the use of db_rewrite_sql in some of the queries in the evoc module (it is also manifested in the rddcck module).

If the i18n module is enabled then when db_rewrite_sql is called the i18n_db_rewrite_sql hook is going to be executed, and that function makes an assumption about the module using db_rewrite_sql(). The i18n hook implementation adds a WHERE clause to the query with the assumption that the table that is being accessed contains a language column. For example, in this line of code:

$res = db_query(db_rewrite_sql('SELECT * FROM {evoc_rdf_classes} WHERE prefix="%s" AND id = "%s"'), $class['prefix'], $class['id']);

The i18n module will evaluate the query and add the following where clause:

WHERE (n.language ='en' OR n.language ='' OR n.language IS NULL)

Since the evoc_rdf_classes table does not have a language column the query will fail. There is a similar query on rdf_evoc_properties which fails.

To fix this in the evoc module a language column needs to be added to both tables and the sql need to be modified as follows:

in line 281, change
SELECT * FROM {evoc_rdf_classes} WHERE prefix="%s" AND id = "%s"'
to
SELECT n.* FROM {evoc_rdf_classes} n WHERE n.prefix="%s" AND n.id = "%s"'

in line 302, change:
SELECT * FROM {evoc_rdf_properties} WHERE prefix="%s" AND id = "%s"
to
SELECT n.* FROM {evoc_rdf_properties} n WHERE n.prefix="%s" AND n.id = "%s"