Hi guys i fixed this problem . please follow this http://developer.linkedin.com/thread/3255 my main reason/problem was my xml was not in the below format and scope was not enabled that is "w_message".
<?xml version='1.0' encoding='UTF-8'?>
<mailbox-item>
<recipients>
<recipient>
<person path="/people/id=T4sKMZ8qEN" />
</recipient>
</recipients>
<subject>Invitation to Connect</subject>
<body>Please join my professional network on LinkedIn.</body>
<item-content>
<invitation-request>
<connect-type>friend</connect-type>
<authorization>
<name>NAME_SEARCH</name>
<value>1Mlb</value>
</authorization>
</invitation-request>
</item-content>
</mailbox-item>