Are you saying that both product-price and stock-level imports fail?
I think you may have got your database into a weird state. Have a look at your node, uc_products and uc_product_stock tables. If you look at sites/all/modules/uc_stock_update/uc_stock_update.module you'll see the SQL "where" clauses involved - it's not particularly complicated and you should be able to figure out what's wrong by experimenting with a few SQL selects.
If it all looks OK, try doing an SQL update manually - it's possible that your database was not restored correctly and all updates on those tables are failing.
By the way, reinstalling the uc_stock_update module won't help here.