Dissapearing changes in subtheme

Hello! When I add my css files and templates I see changes that I made in my new theme. But some time later all my changes disappear and I see:
• Notice: Undefined index: drupal_theme_initialize() (line 100 in file …/includes/theme.inc).
• Notice: Trying to get property of non-object in function_drupal_theme_initialize() (line 146 in file … /includes/theme.inc).
• Notice: Undefined index: myat in function drupal_theme_initialize() (line 100 in file … /includes/theme.inc).
• Notice: Trying to get property of non-object в функции _theme_load_registry() (line 335 in file theme.inc).
• Notice: Undefined index: myat in function theme_get_setting() (line 1431 in …. theme.inc).
Myat is the name of my subtheme
Here is the text from this files
line 100: _drupal_theme_initialize($themes[$theme], array_reverse($base_theme));
lines 93-100
:
// Find all our ancestor themes and put them in an array.
$base_theme = array();
$ancestor = $theme;
while ($ancestor && isset($themes[$ancestor]->base_theme)) {
$ancestor = $themes[$ancestor]->base_theme;
$base_theme[] = $themes[$ancestor];
}
_drupal_theme_initialize($themes[$theme], array_reverse($base_theme));
2)Notice: Trying to get property of non-object в функции _drupal_theme_initialize() (line 146
$theme_path = dirname($theme->filename);
May be I have wrong names of dirictories Т.е. у меня возможно неправильное название директории?
Can it be because I have mu subtheme in folder custom (sites/all/themes/custom/myat)?
3)Notice: Trying to get property of non-object в функции _theme_load_registry() (line 335
return new ThemeRegistry('theme_registry:runtime:' . $theme->name, 'cache');
lines 229-335:
/**
* Gets the theme_registry cache; if it doesn't exist, builds it.
*
* @param $theme
* The loaded $theme object as returned by list_themes().
* @param $base_theme
* An array of loaded $theme objects representing the ancestor themes in
* oldest first order.
* @param $theme_engine
* The name of the theme engine.
* @param $complete
* Whether to load the complete theme registry or an instance of the
* ThemeRegistry class.
*
* @return
* The theme registry array, or an instance of the ThemeRegistry class.
*/
function _theme_load_registry($theme, $base_theme = NULL, $theme_engine = NULL, $complete = TRUE) {
if ($complete) {
// Check the theme registry cache; if it exists, use it.
$cached = cache_get("theme_registry:$theme->name");
if (isset($cached->data)) {
$registry = $cached->data;
}
else {
// If not, build one and cache it.
$registry = _theme_build_registry($theme, $base_theme, $theme_engine);
// Only persist this registry if all modules are loaded. This assures a
// complete set of theme hooks.
if (module_load_all(NULL)) {
_theme_save_registry($theme, $registry);
}
}
return $registry;
}
else {
return new ThemeRegistry('theme_registry:runtime:' . $theme->name, 'cache');
}
}
Should I create a separated cash for my theme? How?
May be I should uncomment some lines?
What does it mean the theme registry?

4)Notice: Undefined index: myat in function theme_get_setting() (line 1431
$theme_object = $themes[$theme];
Lines 1427-1447:
// Get the values for the theme-specific settings from the .info files of
// the theme and all its base themes.
if ($theme) {
$themes = list_themes();
$theme_object = $themes[$theme];
// Create a list which includes the current theme and all its base themes.
if (isset($theme_object->base_themes)) {
$theme_keys = array_keys($theme_object->base_themes);
$theme_keys[] = $theme;
}
else {
$theme_keys = array($theme);
}
foreach ($theme_keys as $theme_key) {
if (!empty($themes[$theme_key]->info['settings'])) {
$cache[$theme] = array_merge($cache[$theme], $themes[$theme_key]->info['settings']);
}
}
}