These sound mostly (or perhaps entirely) that Elgg is trying to run the same upgrade script more than once.

Perhaps this is because Elgg did not finish the upgrade last time because of the .htaccess error.

Can you restore your database to its previous state and try again?

Ah,

I just read that you had done a restore.

But it looks like the restore didn't work then.

You are getting these errors because you are running the upgrade script on a database that has already been mostly upgraded.

...maybe I had accidentally run the upgrade before I did my backup?

I made sure to delete all the tables before I did this restore.

What I'm still confused about is why some new 1.5-specific tables still remain missing missing. Does the script quit trying to upgrade the database upon these errors?

I don't see why it would.

If there is no hope of recovering your previous database, no need to panic yet. I would just identify the missing tables in

engine/schema/mysql.sql

and run that code in phpMyAdmin.

Alright, thanks.

I'll give that a shot.

After upgrading I see two things:

1. Unable to entry to admin/plugins.

2. Unable to save blog post.

Any ideas?

Have you disabled your theme?

I can't to disable theme because I have not possibility to view the plugin page after upgrading

Also unable to save private messages.

Try rmoving the active theme plugin from your mod folder. Then clear your cache, that should put you on the default theme. See how it looks then.