One of the problems that you may have while upgrading CS-Cart is that the upgrade inexplicably fails during the upgrade process. If you are lucky, you will get a error trace umped to a file or the screen. If not, it may just silently fail in the background or freeze up.
This is certainly no fun. There’s a number of different carts that experience this, so it is not limited to just CS-Cart by any means.
Before you attempt any upgrade of your system, it is best to create a development (beta) area for you to test out the upgrade in first. You can do this by copying your files to a new directory or domain / dedicated IP address.
Then, per CS-Cart’s discussions on this topic, edit your PHP.ini file to increase the following values:
Increase the PHP Execution time to 6400
I would also increase memory_limit to 256MB or 512MB depending on how much you can spare.