Well, I know I have run this command numerous times already:

stsadm -o addwppack -filename <abc.cab> -globalinstall -force

But today, when I tried to run this command again, I got the message:

Object reference not set to an instance of an object

Webpart deployment failed.

The first thing I thought of is permission issue, I am running this command with an logged in account which is a member of the administrators group on both the WFE and SQL Servers but this account is not the same as the database access account I used when going thru configuration wizard. So I just go to Central Administration and added myself to have full control to the web application that I am interested at and also added myself to be part of the farm administrator group. (That should really do the trick - I thought to myself)

No luck. Same error message.

Added myself to be part of the security groups related to MOSS on WFE?

Still...... No luck.

Next, I went into SQL Server. I noticed that the logged in account I used don't have any access at all to the admin_content database, so I added the account as db_owner to admin_content.

YES! This works!

Really, new things learned in every brand new day