Wierd errors

Hello there,

I am currently working on a custom theme, all was going well until I changed the Administration theme to Garland. Now my theme no longer displays ANY CSS and it's spitting out a number of errors, of which are below.

* warning: Invalid argument supplied for foreach() in C:\xampp\htdocs\mywebsitedev\includes\theme.inc on line 463.
* warning: Invalid argument supplied for foreach() in C:\xampp\htdocs\mywebsitedev\includes\theme.inc on line 468.
* warning: array_map() [function.array-map]: Argument #2 should be an array in C:\xampp\htdocs\mywebsitedev\modules\system\system.module on line 966.
* warning: array_keys() [function.array-keys]: The first argument should be an array in C:\xampp\htdocs\mywebsitedev\includes\theme.inc on line 1762.
* warning: Invalid argument supplied for foreach() in C:\xampp\htdocs\mywebsitedev\includes\theme.inc on line 1762.

I've never come across these before, what have I done wrong?

Thankyou for your time.