Authentication Error - Shop

[Charl]

I recently updated my development site to 2.0.18a and had to remove all VM data after a DB error due to a dubious plug-in. I used the "Remove Virtuemart Data" tool to do this. Since then I cannot access the "Shop" button and it gives me the following error message  "Authentication Error : Cannot be authenticated using".  If I go to the "Shopper" list and try to edit the admin user (Joomla administrator) I get the same error.

Any ideas on how to resolve this? 

[jenkinhill]

As you have removed all category, product data etc I would suggest a reinstall of VirtueMart, as maybe something else was damaged by your plugin?

Information on the database tools is in the docs - http://docs.virtuemart.net/manual/22-tools-menu/70-tools-migration