big problem to connect to ioftpd

[Roscoe]

Hi everybody, got a big problem.

For the last 3 days, i have the problem that i cannot connect to my ioftpd.
In my client i receive the following error:

network subsystem is unusable 10091.

No firewall is blocking, i have nothing changed.
No antivirus which makes problems.

other external users cannot connect to my ftpd, too.

any ideas?