I had the same problem after I updated. Here's how you fix it:
Go to Components->Hikashop->Configuration in the back end of your site, click on the 'Display' tab, and on the left side of the screen somewhere you should see an option that says "After a product is added to the cart". Click on the drop-down list next to this option and select "Always stay on the same page". That should solve your problem.
This is what it should look like (the option you need to change is in a red circle):
EDIT: Make sure to save the configuration so that the changes are applied.