cannot open shared file

There are several files on another XP computer on a peer network. I can see them but get an error (access denied) when trying to open them. The properties of the files have been checked to allow 'other users to change'. This seems to work some days but is not consistent. Today is one of those days when I cannot open them. The files are not open and are not protected in any way. Any thoughts?

Can you do things with the files other than opening? Such as copy one to your PC (and if so, will it open there?) or making a copy on the other PC and opening the copy?

Specific files or file types or just a general problem?