weird unserialize issue in 1.3 alpha

Notice: unserialize() [function.unserialize]: Error at offset 6 of
1051 bytes in C:\xampp\htdocs\projects\courses\cake\libs\cache
\file.php on line 189

anyone seen that before? I have 5 similar warnings all because the
same line. I am on a windows machine running xampp.

when i click notice the error reads:
Code | Context

$key = "cake_core_file_map"
$time = 1262723833
$cachetime = 1262723843
$data = "a:6:{s:4:\"Core\";a:6:{s:6:\"Router\";s:53:\"C:\xampp\htdocs
\projects\courses\cake\libs\router.php\";s:13:\"ClassRegistry\";s:
61:\"C:\xampp\htdocs\projects\courses\cake\libs\class_registry.php\";s:
12:\"Overloadable\";s:59:\"C:\xampp\htdocs\projects\courses\cake\libs
\overloadable.php\";s:8:\"Security\";s:55:\"C:\xampp\htdocs\projects
\courses\cake\libs\security.php\";s:4:\"l10n\";s:51:\"C:\xampp\htdocs
\projects\courses\cake\libs\l10n.php\";s:4:\"i18n\";s:51:\"C:\xampp
\htdocs\projects\courses\cake\libs\i18n.php\";}s:10:\"Controller\";a:4:
{s:9:\"Component\";s:67:\"C:\xampp\htdocs\projects\courses\cake\libs
\controller\component.php\";s:10:\"Controller\";s:68:\"C:\xampp\htdocs
\projects\courses\cake\libs\controller\controller.php\";s:
13:\"AppController\";s:72:\"C:\xampp\htdocs\projects\courses\cake\libs
\controller\app_controller.php\";s:15:\"PagesController\";s:74:\"C:
\xampp\htdocs\projects\courses\cake\libs\controller
\pages_controller.php\";}s:4:\"View\";a:2:{s:6:\"Helper\";s:58:\"C:
\xampp\htdocs\projects\courses\cake\libs\view\helper.php\";s:4:\"View
\";s:56:\"C:\xampp\htdocs\projects\courses\cake\libs\view\view.php\";}
s:9:\"Component\";a:1:{s:16:\"SessionComponent\";s:76:\"C:\xampp\htdocs
\projects\courses\cake\libs\controller\components\session.php\";}s:
6:\"Helper\";a:4:{s:9:\"AppHelper\";s:70:\"C:\xampp\htdocs\projects
\courses\cake\libs\view\helpers\app_helper.php\";s:10:\"HtmlHelper\";s:
64:\"C:\xampp\htdocs\projects\courses\cake\libs\view\helpers\html.php
\";s:10:\"FormHelper\";s:64:\"C:\xampp\htdocs\projects\courses\cake
\libs\view\helpers\form.php\";s:13:\"SessionHelper\";s:67:\"C:\xampp
\htdocs\projects\courses\cake\libs\view\helpers\session.php\";}s:
10:\"Datasource\";a:2:{s:9:\"DboSource\";s:75:\"C:\xampp\htdocs
\projects\courses\cake\libs\model\datasources\dbo_source.php\";s:
8:\"DboMysql\";s:78:\"C:\xampp\htdocs\projects\courses\cake\libs\model
\datasources\dbo\dbo_mysql.php\";}}"

unserialize - [internal], line ??
FileEngine::read() - CORE\cake\libs\cache\file.php, line 189
Cache::read() - CORE\cake\libs\cache.php, line 306
App::getInstance() - CORE\cake\libs\configure.php, line 967
App::path() - CORE\cake\libs\configure.php, line 621
Configure::__loadBootstrap() - CORE\cake\libs\configure.php, line 416
Configure::getInstance() - CORE\cake\libs\configure.php, line 60
include - CORE\cake\bootstrap.php, line 38
[main] - APP\webroot\index.php, line 76