here are updated copies of the following pages that should correct the problem:
webassist/plugins/catalog/results.php
webassist/plugins/catalog/results_grid.php
webassist/plugins/catalog/basic/results.php
also run the following query on the database:
CREATE INDEX ProductID ON ps4_products(ProductID);
CREATE INDEX ProductID ON ps4_productoptions(ProductID);
CREATE INDEX ProductID ON ps4_productcategories(ProductID);
CREATE INDEX CategoryID ON ps4_productcategories(CategoryID);