Curier-IMAP and imap.create()

I don’t get imap.create to work on Courier-IMAP. I can search
mailboxes etc. But not create. Tried to create on another imap account
and that worked (don’t know what imap server is used here).

Here is the error message:
“$ ./imap-copy.rb
/usr/lib/ruby/1.8/net/imap.rb:971:in get_tagged_response': Invalid mailbox name. (Net::IMAP::NoResponseError) from /usr/lib/ruby/1.8/net/imap.rb:1022:insend_command’
from /usr/lib/ruby/1.8/monitor.rb:229:in synchronize' from /usr/lib/ruby/1.8/net/imap.rb:1007:insend_command’
from /usr/lib/ruby/1.8/net/imap.rb:414:in `create’
from ./imap-copy.rb:19”

Do anybody know how to create folders on courier-imap servers/ why it
doesn’t work for me?

Regards,
Henrik