Opening Excel Attachment from Outlook 2003

I have just started having a problem where I cannot access Excel files sent to me. I run Outlook 2003, and when I try to open or save the attachment I get the following message :

Can’t create file: Filename.xls, Right-click the folder you want to create the file in, and then click the shortcut menu to check your permissions for the folder

I have tried ‘detect and repair’ from Outlook help, and have deleted the contents of the temporary internet files folder.

Any ideas what else it could be?

Thanks