Roundcube login problem

[galactica132]

Hello all!
I cannot login in roundcube with a newly created mailbox user. I have enabled imap debugging and the output is like this(before was working everything fine):
[11-Jul-2012 13:35:25 +0400]: [330E] C: A0001 LOGIN username@domain.tld ***PASSWORD***
[11-Jul-2012 13:35:25 +0400]: [330E] S: * BYE [ALERT] Fatal error: No such file or directory: No such file or directory
These were the roundcube imap error loging outputs.
Now the errors file:
[11-Jul-2012 13:35:25 +0400]: IMAP Error: Login failed for username@domain.tld from **IPADDR**. LOGIN: Fatal error: No such file or directory: No such file or directory in /var/www/webmail/program/include/rcube_imap.php on line 205 (POST /webmail/?_task=login&_action=login)
..
What could be the problem thank you in advance for your help!

[falko]

Did you send an email to the new account before you tried to log in? The relevant directories are created automatically when the first mail arrives.

[galactica132]

Yes i have tried sending an email to the adress and it say that cannot connect to the imap server when i am trying to login. But the email adresses which were created before are working without problems, I can login ,send and receive emails... So i do not know what could be the problem

[galactica132]

UPDATE
ISPCONFIG cannot write any changes to disk... if i create new vhost then it is not appearing in /etc/nginx/sites-available nor in /etc/nginx/sites-enabled.... what could be the problem or which logs should I post?

[falko]

Are there any errors in ISPConfig's monitor module?

Which tutorial (URL) did you use to set up the system?