Can't copy to FTP: Socket is not connected

I've been using DirOpus for a few years now so I had a well established workflow.
However something happened in the past 14 days which prevents me copying
files to ftp. I think I updated DirOpus but I'm not sure, I'm on (4779).
(I'll update as soon as possible but right now I can't restart my pc.)

Anyway, when I drag and drop files from local hdd to FTP site it says
"The directory of file cannot be created (82)".

The FTP log contains this:

SendFtpCmd() - WSAENOTCONN: Socket is not connected
** WSA returns ERROR **
** WSAENOTCONN Connection Lost!

Refreshing the view works but copying from ftp fails the same way.

Have you tried everything in the FTP FAQ?

Right, so I can't even connect with FileZilla... something is weird at the other end it seems.

After changing my account password on my website management page now
I can connect and copy with FileZilla. With DirOpus I can log in, list contents
but still can't copy. Turned passive mode off but that didn't change anything.
I disabled both windows 7 firewall and MS Security Essentials, no help.
I don't have a proxy.
I CAN copy to a different FTP server (different company, different country).

Should I ask something from my web space provider?

I was finally able to restart the machine and the issue is now gone.