A user had this problem with a database I had written. Service desk thought it was to do with the database. The error "File cannot be created" came up just after a new document was composed, before any typing or saving. Deleting cache.dsk solved it temporarily.The Postopen event had code in but not files were being created.

A previous Notes expert had tried deleting the cache.dsk file. This fixed the problem temporarily.

I found the permanent answer in the knowledge base.

The user had to:

Close Notes.

Then in windows explorer make sure "Show Hidden files" is ticked on.

(Go to Tools>Folder Options, Select the view tab, then under hidden files and folders check "Show hidden files and folders" )

The user had to find the directory called c.Notes.Data  or similar.

Searching for *Notes.Data*.* seems to work.

Delete this and then restart Notes. This did the trick.

This directory or a file in it had obviously become corrupted.