Symptoms

Some documents in some spaces cannot be edited using viewfile macro or from the attachments view functionality. This only affects attachments in some spaces where the page hierarchy to the page is quite deep leading to a long path name in Webdav. You may find however that editing the same file in Mac OS work.

Cause

This is caused by a limitation in Microsoft Webdav where a path to an attachment is longer than 260 characters. This issue has been filed as a bug report in the Webdav plugin project: WBDV-52. Note that the url mentioned is not the url seen from the internet browser, but the url used for the Webdav connection.

Resolution

Rename your page title to something shorter. To know how long the webdav url is, you can access the file via webdav, copy the url, decode it and calculate.
There is a good discussion on this in a blog article by Tim Jones.