Windows 7 - Strange EFS behavior (not a FAQ)

Hello,

I am using EFS with a self-signed certificate for about a year -- no issues so far. I work on Windows 7 Enterprise.

Very recently I started to have a strange behaviour of the encrypted folder:
- I CAN create new files (encrypted)
- I CAN read old encrypted files
- I CAN copy files from/to the encrypted folder
- but I CANNOT save files to this encrypted folder from within an application (MS Word for instance, and other non-MS software). I get a "you don't have permissions to save here" message. This includes existing files i would like to edit and save in the same place afterwards (saving somewhere else is fine)

I suspect an issue with the certificate but do not know how to check it. I ran the "manage file encryption certificates" wizard which mentionned the existing certificate, valid until 2110.
Maybe something to do with the recovery certificate? How to check that one?

Thanks in advance for any pointers,
WoJ