can’t do network attachment(outlook 98)

I have a user working on Win 98 pc with Outlook 98. Recently the user claimed that he can’t insert attachment from network drives.(the file size is small, around 100 kb). The error msg is “The system cannot find the specified path”. But the user can see the file from the “Insert File” box. There is definitely no problem with the network as the user copy and paste the file into outlook. Can anyone helps? Thanks!