This is a niggle I've had with Opus for a long time. When I try to copy files on my FTP, via a standard port 21 connection, from one FTP folder to another FTP folder Opus always pops up with an error message. If I then press the copy button again it copies the files just fine 
What error message? What do the FTP logs say?
Sorry, I was being lazy and should have been more specific.
Opus pops up the following error message, check out the attachment for the snapshot.
In the Logfile it reads:
[quote]220 Ftp server ready.
331 User xxxxxxx okay, need password.
230-You are user #162 of 550 simultaneous users allowed.
230-
230 Restricted user logged in.
200 Type okay.
257 "/" is cwd.
250 "/xxx/xxxxx/xxxxxxx" is new cwd.
257 "/xxx/xxxxx/xxxxxxx" is cwd.
227 Entering Passive Mode (xx,xxx,xxx,xxx,xxx,xx)
550 Data connection must go to same host as control connection.
Connection closed
[/quote]
I hope that better information 
That means the site is explicitly blocking site-to-site FTP transfers.
When it then works the second time it's probably because Opus falls back on copying the data to your PC and then to the other server, rather than directly from server to server.
To avoid the error and always copy via your PC, edit the FTP bookmark entry and turn off the Site-to-Site options on the Network tab.
It's amazing how much quicker and easier questions can be answered when they are accompanied by a clear and thorough presentation of the relevant facts.
Thanks for the info, that probably explains it. I'm just glad that I eventually managed to provide "a clear and thorough presentation of the relevant facts."