Step 2 Error while importing from b2

I have search the forums for topics related to this but found no solution. I was importing my b2 to wordpress and I run the import-b2.php file on my server. In step 2, there was this error…

WordPress database error: [Duplicate column name ‘post_excerpt’]
ALTER TABLE wp_posts ADD COLUMN post_excerpt text NOT NULL;

WordPress database error: [Duplicate column name ‘post_status’]
ALTER TABLE wp_posts ADD post_status ENUM(‘publish’,’draft’,’private’) NOT NULL, ADD comment_status ENUM(‘open’,’closed’) NOT NULL, ADD ping_status ENUM(‘open’,’closed’) NOT NULL, ADD post_password varchar(20) NOT NULL;

That went well! Now let’s clean up the b2 database structure a bit…

WordPress database error: [Can’t DROP ‘ID’. Check that column/key exists]
ALTER TABLE wp_posts DROP INDEX ID

One down, two to go…

So far so good.

WordPress database error: [Can’t DROP ‘post_karma’. Check that column/key exists]
ALTER TABLE wp_posts DROP post_karma

Almost there…

WordPress database error: [Can’t DROP ‘ID’. Check that column/key exists]
ALTER TABLE wp_users DROP INDEX ID

Does anyone know the reason behind this error and how to fix it? Help will be appreciated. Thank you… =)