RBS Worldpay payment system has announced some changes on their website:
http://www.rbsworldpay.com/support/bg/index.php?page=news&sub=xss
 
The one concerning ViArt is the new Payment URL which is recommended to change in your shop for better interaction with Internet Explorer 8.
 
You may want to go Administration > Orders > Payment Systems > Edit WorldPay and change the Payment URL to this one:
https://secure.wp3.rbsworldpay.com/wcc/purchase
 
The old Payment URL will continue to work and will represent a page with a redirect button which customers should click to be transferred to RBS WorldPay payment pages. The new Payment URL sidesteps this additional page and forwards customers straight to payment pages.