Can't open 'services for object' with Gui HTML in IE

Hi experts,

with our new process we want to approve MM purchase orders in our portal. To approve the PO I use the link in the protal, PO is opening with Gui Html and the approver is able to check all items and values in the PO. We also use attachments and normally I'm able to check the attachments within 'services for object' => Attachment list. This works with Firefox but not with IE10 or Chrome.

Approval process always takes place in our portal, most of the approvers don't have access to SAP Gui!

Any idea how to solve this also for other browsers?

Thanks

Hubert