I am going to upgrade JIRA 5.2 to JIRA 6.4. I am upgrading manually.
What i did is install new JIRA. Import the XML back up. All data is imported successfully in new JIRA and it is running perfectly fine. Hurrah! 
But when i point JIRA home to old on problems begins. 
When i start jira it stucks here [atlassian.plugin.util.WaitUntil] Plugins that have yet to be enabled: (23):
It start from 49 plugins and hangs at 23. I have read all the articles and done all the remedies.
- Disable antivirus
- Remove plugin cache from JIRA home
- Setting these parameters -Xms512m -Xmx1024m -XX:MaxPermSize=512m
- Increasing plugin load time -Datlassian.plugins.enable.wait=30000000
Ya it is 30000000 
Some one has any idea ?
Thanks in advance.