We show a list of users in a paginated fashion (10 rows per page). There is a column to flip the status of an user to activate or disable. Assuming I am in the 3rd page and I am disabling a user. After performing the action, should I re-load the paginated user list with the 3rd page or should I re-direct to the first page.
Think of the question another way. If you were editing an text document, and you were on the 3rd page, when you decided to delete a word. Would you want the program to take you back to the first page, or let you continue from where you are?
The answer is clearly that you would want to continue from where you are, and the same thing applies to list - which are just a different type of content. If you edit an item in the list, you should remain in the same position after the edit.
However, how you handle showing the item is murkier. If the list only shows active users, then you would have a case for removing that user from the list. In this case I would suggest adding the next item in the list beyond the page you are on to the bottom of the page. If you don't do this, it often becomes unclear what you should show when you show the next page. Should you show items 31-40 or items 29-38 (if you deactivated two before). oDesk has this particular problem.
The alternative that I would suggest would be to keep the item in the list, and simply show the item as disabled. That way if you accidentally disabled a user, you can easily correct the problem. It also means that you have a simpler pagination.