Price for a particular shopper group doubles in shopping cart

[psychologynj]

Recently, any purchase by someone in our Members shopper group is doubling the retail price when the item is put into their shopping cart.  This does not happen for other shopper groups.  This was not an issue in the past.  I'm not sure if this is due to a recent update to VM.  I am using VM 2.6.14 and J2.5.28.   Any assistance would be appreciated!

Thanks Christine