6
User your database toolset (phpMyAdmin, maybe) to run the following mySQL command:
UPDATE 'xoops_config'
SET conf_value='oldthemename'
WHERE conf_name='theme_set';
oldthemename is the name (aka directory) of your old theme. And if you use a different 'prefix' than 'xoops' for your tables, then you should use 'prefix_config' for the table name.
This will get you back up and running. Then, to test out new themes, enable the theme chooser block in the blocks administrator for admins only and in the preferences, set it so you can change the themes amongst those you want, but leave the current good one default. Then you can test it out that way (and use two different browsers, maybe). Also, if the theme doesn't work, backing up a page using the browser navigation puts you back to the original theme.
Hope that helps.
