Internal Server Error

[محروم.كوم]

hello guys
i received this error when i running passwordcheck.php in admin panel
Code:
Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator* [email protected] and inform them of the time the error occurred* and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally* a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
i checked my .htaccess
Code:
RewriteEngine On
RewriteRule ^([a-z0-9_\-]*-(f|all)[0-9]+(p[0-9]+|/index[0-9]*)?\.html)$ forumdisplay.php/$1 [QSA*L]
RewriteRule ^([a-z0-9_\-]*-(t|p)[0-9]+(p[0-9]+|/index[0-9]*)?\.html)$ showthread.php/$1 [QSA*L]
RewriteCond %{REQUEST_URI} !(index\.php|\.css) [NC]
plz help my about resolve this problem.
tank you __DEFINE_LIKE_SHARE__