In PhpMyAdmin of a MySQL console you should do a
Code:
SHOW CREATE TABLE db_cache;
(db_cache may be zen_db_cache or some other prefix you have chosen) and the column
cache_data should show up as a mediumblob the code in the Zen Cart install sql is
Code:
DROP TABLE IF EXISTS db_cache;
CREATE TABLE db_cache (
cache_entry_name varchar(64) NOT NULL default '',
cache_data mediumblob,
cache_entry_created int(15) default NULL,
PRIMARY KEY (cache_entry_name)
) TYPE=MyISAM;
so there's no reason why it should be a BLOB and not a mediumblob if it has been a fresh install then you may have some issue with your version of MySQL or your host may have done something to the configuration. (though I have no idea if it is possible to compile MySQL without large BLOB support). If it is a MySQL configuration problem then you shouldn't be able to change it using the ALTER TABLE sql above.
Philip.