Thank you for your reply.
Yesterday I have followed above step but the problem is still exist. the menu is still disappeared.
This problem also occurred on some other application especially java application (jar).
So i guess the problem comes from BB OS6.

This morning I get update (again) from RIM and installed OS-6 version 6.0.0.488 (previous version is 6.0.0.380). I updated my OS6 and everything is OK now. I can see again the menu when I press BB menu.

could you please remove the app and all tmp files before reinstalling it?
(1) Close the app
(2) Open the Media application on the BlackBerry
(3) Press the Menu button and choose Explore
(4) Navigate to folder //store/home/user/ and/or to //SDCard/BlackBerry/
(5) Select the folder wordpress/
(6) Press the Menu button and choose Delete
(7) reinstall the app using our download page

When the installation is complete, go to Options->Applications. Scroll through the list, highlight and select “WordPress”. Next, click on the app, and choose Edit Permissions and ensure they are set to “Allow”.
If you have changed the permission settings,you must reboot the phone by removing and reinserting the battery.

I used wordpress for Blackberry in my Curve 3G (9300) with BB OS 5 and it worked fine, everything is OK.
Yesterday I upgrade my OS to BB OS 6, and when I tried to write a new post, it''s nothing happen when I press BB menu. The menu is gone.
I tried to reinstall the application, but not help.
Can anyone help me how to fix this.
Thank you.