When I upgraded to NetBlog 1.5.1 from 1.4.4, my widgets went haywire. I was unable to undo the damage until I had deactivated and deleted NetBlog files and data.
Some widgets I had in one sidebar were bounced to another sidebar -- my theme has 9 sidebars. Other widgets disappeared entirely. Some widgets were more helpfully bounced to the Inactive Widgets tray so their settings were preserved, in those cases.
Before upgrading, I had 30-odd widgets in 9 sidebars and settings in each, so I lost a fair amount of configuration work when the widget bomb went off on upgrade to 1.5+. I did not back up everything before clicking through the automatic upgrade to the plugin -- my bad, I should have checked what all the changes were and seen potential conflicts in advance.
I'm using a child theme of BuddyPress Daily 3.4, http://premium.wpmudev.org/project/buddypress-daily-theme on WP 3.0.1 multisite with BuddyPress. I don't expect NetBlog to support this or all themes, I'm just reporting the issue. Love NetBlog and hope to get it back someday!