Fatal error: Call to undefined function get_current_screen()

I have a new WP install. 62 different pages, a little blog distributed around based on category. I’ve installed the e-commerce plug-in, added a few products. Still testing…

I keep everything in it up-to-date, checking for updates at least twice daily. I’m hosted on Dreamhost.

I haven’t yet gone live with the site (it’s filled with Latin text right now) because there is a weird error I keep getting.

Error #1:

1. In the Dashboard, I click [Appearance] >> [Edit CSS]
2. In the CSS window, I make a change, such as p {color:pink;}
3. I click [Save Stylesheet]
4. I receive an error message that reads:
Fatal error: Call to undefined function get_current_screen() in /home/edwardmartiniii/testy.hellbendermedia.com/wp-content/plugins/wp-e-commerce/wpsc-admin/includes/product-functions.php on line 23
5. So, I click the BACK button on my browser, and once again click [Appearance] >> [Edit CSS]
6. My change is not present.
7. So, I open the described file “product-functions.php”. Line #23 reads:
$current_screen = get_current_screen();
8. Meaning I can’t edit the CSS programmatically. I don’t know what this function is SUPPOSED to be doing, and I don’t know why editing the CSS calls a function in the e-commerce module anyway.
9. Troubleshooting suggestions welcome! I could MANUALLY edit the CSS file and then upload it, but I’m afraid any changes I make will simply be lost in the next update.

Thanks!

Edward