Both Gallery and WordPress use the function stripslashes_deep.
To get rid of the redeclaration error I had to edit util.php in the Gallery directory.
Replace:
function stripslashes_deep($value) {
$value = is_array($value) ? array_map('stripslashes_deep', $value) : stripslashes($value);
return $value;
}
With:
if (!function_exists("stripslashes_deep")) {
function stripslashes_deep($value) {
$value = is_array($value) ? array_map('stripslashes_deep', $value) : stripslashes($value);
return $value;
}
}