Comment on WordPress Widgets Tutorial by Abel.

WordPress SEO Widget Hi David,
After moving from another theme to Stallion, the previous widgets can still be seen in the sidebar, but I am unable to open any of them in the widgets page to delete (sitting as text widgets) or add any new ones. It seems like some kind of corruption, can you please advice?

I can’t drag the items in a menu structure up/down/or sideways. A list of blank doted blocks appears. I can do this on another site so it doesn’t look like is related to the WP version or the browser. Any suggestions please?