SSHFS - suddenly no write

Hi there, I have been using sshfs for years on a server without incident. Now when I connect I can't write to / save the PHP files I am editing. The server shows the following error: sftp-server[34002]: error: process_write: write failed I have checked the disk for space (there is plenty and I have even deleted files). The permissions have not changed and I have tested and reset them on various directories. Geany: Error saving file. Nautilus: Error creating directory: Operation not permitted Any ideas how to debug? I think it is specific to this server. Thanks Piers