After migrating to a new server, we where getting the following open_basedir restriction errors from wp-e-commerce v 18.104.22.168.
Warning: file_exists() [function.file-exists]: open_basedir restriction in effect. File(.../plugins/wp-e-commerce/wpsc-theme/) is not within the allowed path(s): .../plugins/wp-e-commerce/wpsc-core/wpsc-constants.php on line 301
...on line 307
We solved this issue by removing the wpsc_selected_theme entry from the wp_options table like so:
Delete FROM wp_options WHERE option_name = 'wpsc_selected_theme'
This is a workaround for less than optimal architecture of the wp-e-commerce plugin. Hope it helps someone.