Error when sending invoices via email

SOLVED

Hi all,

I suddenly have a problem when sending invoices via email.  This worked fine last week but now I get the message:

Error with the address xxxxxx  Unknown Error. Please check Windows Event Log for more details.

The event log says:

Error sending email using Outlook : System.IO.DirectoryNotFoundException: Path does not exist. Verify the path is correct.
at Microsoft.Office.Interop.Outlook.Attachments.Add(Object Source, Object Type, Object Position, Object DisplayName)
at Sage.Email.Outlook.OutlookMailer.SendMailInternal(Email email, SendMailOption whenToSend)
at Sage.Email.Outlook.OutlookMailer.SendMail(Email email, SendMailOption whenToSend)

I've tried various different email templates that I use and they all have the same issue.  I've not changed any email settings. 

Any help would be greatly appreciated! 

Many thanks

Paul