ITS server not working for some machine's

Hi

We have two ITS Systems for our production SRM system .For some people they are not able to downlaod the attachment from the shoping cart . Its says page cannot be displayed or couldnt establish the connection with server . Its really weird because the same user can login to different system and he is able to download the attachmnet. i don't think this would be local machine problem since it's working last week. can anybody provide a help in this

Regards

MA.Sreenivasan