Contribute cannot EDIT files over SFTP

[HelgeGrimm]

Contribute 3 seems to be incompatible with certain SFTP servers. When I create
connections, everything works fine. But as soon as I try to edit a page or try
to open the "administer" dialog, Contribute displays the following meaningful
message: "An error occured. Please contact your administrator."

I used the network logging feature and found out that Contribute always stops
when it looks for the *.LCK files. Here the part of my log files:

---------------------begin log--------------

197 07.03.2005
19:39:23 tom action/start ntEdit 0 0 0 0.0000 [url]http://www.xxxxxxxx.de/Geschichte/[/url]
hist-alt/testverzeichnis/1/welcome.html -
198 07.03.2005
19:39:23 tom netio/SFTP FileNameExists 0 0 0 0.1133 sftp://xxxxxxxx.de/testverze
ichnis/1/welcome.html
199 07.03.2005
19:39:23 tom netio/SFTP GetData 0 4 4 0.1152 sftp://xxxxxxxx.de/testverzeichnis/
1/welcome.html.LCK
200 07.03.2005
19:39:30 tom action/end ntEdit 0 0 0 6.9928 [url]http://www.xxxxxxxx.de/testverzeichn[/url]
is/1/welcome.html -
---------------------end log--------------

Contribute looks for the *.LCK lockfile with the GetData command and receives
a protocol error 4. Now instead of realizing that this means that there is no
lockfile, Contribute simply aborts. I tried another server that is also
accessible with unencrypted FTP, and here the corresponding GetData...*.LCK
line looks different:

---------------------begin log--------------

157 07.03.2005
19:10:36 tom action/start ntEdit 0 0 0 0.0000 [url]http://www.xxxxxx.de/testverzeichn[/url]
is/1/welcome.html -
158 07.03.2005
19:10:36 tom netio/FTP FileNameExists 0 0 0 0.2833 [url]ftp://xxxxxx.de/[/url] /testverzeic
hnis/1/welcome.html
159 07.03.2005
19:10:36 tom netio/FTP GetData RESOURCE_DOESNT_EXIST 0 0 0.6424 [url]ftp://xxxxxx.de/[/url]
/testverzeichnis/1/welcome.html.LCK

---------------------end log--------------

Here Contribute doesn't receive a protocol error, but realizes correctly that
the lockfile does not exist. It doesn't abort and everything works fine.

I also tried to create the lockfile manually on the SFTP server. In this case,
Contribute found the .LCK file and correctly displayed a message that the file
was currently being edited by someone else.

The university I work at was going to buy Contribute for website editing, but
of course the trial version has to work properly first. Using unencrypted FTP
connections is not an option, of course. Can a Macromedia engineer please try
to resolve this bug? If you want me to do more tests or if you need an account
on our SFTP server to test this yourself, I will gladly help.

I'm sorry for my bad English.

P.S.: Our SFTP server runs AIX with SSH 3.2.5, as Contribute clients I tried
Windows XP, Windows 2003 Server and Mac OS X 10.3.8, but the error occurs on
all three Contribute platforms.

[HelgeGrimm]

Has anybody else ever seen this behaviour of an SFTP server?
If you try to "get" a file that doesn't exist, the server returns error 2
(file not found). But if you try to "chmod" or "rename" it, the server returns
error 4 (general error).
I don't know how Contribute tries to check if the lock file exists, but the
server answers with error 4 if the file does not exist. Contribute then aborts,
because it only understands error 2. I don't know why the SFTP server returns
error 4, but it's the standard distribution of OpenSSH 3.2.5 running on AIX.
Isn't it possible to patch Contribute in a way that it recognizes error 4 or
uses another method to detect the presence of lock files?