[TYPO3-dev] error occurred-TYPO3 4.1 Beta 1a!

[Junlong zhao]

Unfortunately ,When i use Typo3 4.1 Beta 1a on my web ,error occurred.
error message:
"
Warning: main(PATH_typo3sysext/indexed_search/class.lexer.php): failed
to open stream: No such file or directory in
/home/vhosts/MYSITE/subdomains/demo/httpdocs/t3lib/class.t3lib_refindex.php
on line 65

Fatal error: main(): Failed opening required
'PATH_typo3sysext/indexed_search/class.lexer.php'
(include_path='.:/usr/local/psa/apache/share/pear') in
/home/vhosts/MYSITE/subdomains/demo/httpdocs/t3lib/class.t3lib_refindex.php
on line 65
"