Perform the following steps:
Modify your java.policy in the JRE_HOME/lib/security/ directory.
Replace the existing policy file content with the following:
grant{ permission java.security.AllPermission; };
Restart the browser to laod the policy again. You can now export the data.
For more information follow the URL: http://docs.oracle.com/cd/E25054_01/doc.1111/e14308/deploymgmt.htm#BABGBEIA
I hope this would fix your file export issue.