WordPress 2.7 and WP E-commerce plugin “Error 500 – Internal server error” SOLUTION!
WordPress 2.7 + WP E-commerce plugin + 1and 1 hosting causes an “Error 500 – Internal server error” when trying to activate the WP E-commerce plugin.
Solution from the WordPress Support Forums – from member “arapacana” (post #13, from the top):
If Brian’s solution doesn’t work, you can edit or create an .htaccess file to make your php files run with php5, since Apache by default may be running an earlier version of php.
Just put the following in the file on its own line:
AddType x-mapp-php5 .php
The .htaccess file can be in the root directory of your blog or website, and is just a text file.
Hope this helps – it worked for me and others for this problem.