Hi aviskipat,
On our free hosting service, we have a hard limit on the number of files and directories one account can hold, which is set at 50,000 "inodes". It appears your account has hit this limit, which is probably why you are seeing this error message.
I took a quick look at your account, and it appears you have 7,000 old cron emails from 2012-2013 stored on your account. Would you like me to remove these for you? This would free 7,000 inodes.
Thank you,