Shipping and error message

[conceptsk]

I deleted some shipment methods that I didn't use. Since, I have this error message when I want to choose the shipment method:

Info: Unrecognised mathop in calculation rule found, seems you created this rule with plugin not longer accesible (deactivated, uninstalled?)

All working perfectly. My shipping and my taxes are calculating but I have this message.

How can I remove it?

p.s. I am using Virtuemart 2.0.20b and Joomla 2.5.

[jenkinhill]

Similar to http://forum.virtuemart.net/index.php?topic=114032.msg384023#msg384023  ?

[conceptsk]

Yes, I tried tax per product and I don't have the message anymore. But, I need tax per bill because in Quebec, we have two taxes and it is the only way  this 2 taxes appears on the invoice.