Jeff, stock osCommerce doesn't have a "products_stock" table, and stock Easy Popluate doesn't look for that table either. If the code is looking for this table, something must have been modified. Are you running a Linux or Windows server? On Linux I would suggest running a 'grep -l -r "TABLE_PRODUCTS_STOCK" *' command to find out where that table is defined, and which pages are looking for it.
You also mentioned that you're running version 3 of Easy Populate, which has been "disowned" by the author himself. I would suggest using an older version (between 2.8 and 2.9) that stores the configuration variables in the database like most other user friendly contribs.
Tim
By the way, I have a HUGE inventory, and to import and update 100,000 products using a heavily modified Easy Populate (it updates a lot more columns in the database, automatically updates pricing according to a table defined through the admin section, updates inventory hourly and checks for new products weekly through cron), it only takes SIX MINUTES to update every field!