This was a real problem i faced after upgraded wordpress from 2.8 to 2.9 :s. If I try to post a new post, I couldn’t find the publish button. I’m sure many of you facing same problem. same problem faced when upgraded from 2.7 to 2.8 also. Well wordpress neither 2.8 nor 2.9 having bugs in the original codes. It is all because of unsupported plugins to new versions. Let me tell how to solve this problem.
First you need to deactivate all the plugins installed. If you have many plugins installed then you may deactivate all from phpMyAdmin. I know you asking how to do it.
To disable all plugins using phpMyAdmin, login to your cPanel and click phpMyAdmin icon. After that, select your wordpress database that you want to alter.
Images below will appear after you have selected your database.

- Select the wp_options table from your database.
- Turn to ‘Browse’ tab.
- Under the option_name column (field), look for active_plugins.
- Then, click the pencil icon to edit the option_value.
- Go to the option_value text area as highlighted in the above images. Select all the codes inside the area and replace it with a:0:{}
- Click ‘Go’ button to save the setting.
!Note: If you couldn’t find the active_plugins row, click the next button. You will find it on the next page.

OK now you have deactivated all the plugins. Now login to your blog and click “Add New” under Posts. Don’t you see the Publish button in your left side
. Now need to find out which plugin gave us this much trouble. Activate plugins one by and check the Ad New page. I’m sure you will find it
.
Hope this can help you. More info, go to WordPress support forum.
Nice post, learned a lot form here. thank you