Windows and OS-X

I would hazard a guess that the first error may mean that the share was not mounted as writable. Bazaar needs write access in situations like these to perform locking.

The second error suggests to me that you may just have the path to the branch on PC1 wrong. Experiment with sftp until you can determine the correct path to use.

As for the mounting solution: I can write and delete files in /Volumes/PC1branchdir/. The mounting solution works when PC2= Fedora Linux. Might it have something to do with "Bug #313625"?

As for the ssh/sftp solution: it works now using sftp (double // before cygdrive was the problem). However bzr+ssh still gives the same error. I have the same problem when PC2=Linux.

This works:
bzr branch sftp://user@PC1/cygdrive/c/PC1branchdir/

This doesn't:
bzr branch bzr+ssh://user@PC1/cygdrive/c/PC1branchdir/
bzr: ERROR: Not a branch: "bzr+ssh://user@PC1/cygdrive/c/PC1branchdir/".
No handlers could be found for logger "bzr"

Yes, I think it may be related to bug 313625. According to bug 31006, you may be able to configure either Windows or the SMB client on your Mac to allow file locking over SMB shares.

Regarding bzr+ssh not working, when you ssh to PC1 is the 'bzr' command in the PATH?

"/cygdrive/c/Program Files (x86)/Bazaar" is in the PATH.

As for the bzr+ssh problem, I also noticed something which is the core of the problem I think. The problem would be in PC1 (windows+cygwin)

When I am on the command prompt on PC1, then this works:
bzr check c:/PC1branchdir/
<gives repository information>

The log file gives this:
0.063 bzr arguments: [u'check', u'c:/PC1branchdir/']
0.078 looking for plugins in C:/Documents and Settings/Administrator/Application Data/bazaar/2.0/plugins
0.078 looking for plugins in C:/Program Files (x86)/Bazaar/plugins
0.141 encoding stdout as sys.stdout encoding 'cp437'
0.188 opening working tree 'C:/PC1branchdir/'
[13592] 2010-07-10 13:07:59.069 INFO: Checking working tree at 'C:/PC1branchdir/'.
0.203 opening working tree 'C:/PC1branchdir/'
[13592] 2010-07-10 13:07:59.084 INFO: Checking branch at 'file:///C:/PC1branchdir/'.
[13592] 2010-07-10 13:07:59.084 INFO: Checking repository at 'file:///C:/PC1branchdir/'.
[13592] 2010-07-10 13:07:59.147 INFO: checked repository <bzrlib.transport.local.LocalTransport url=file:///C:/PC1branchdir/> format <RepositoryFormat2a>
[13592] 2010-07-10 13:07:59.147 INFO: 8 revisions
[13592] 2010-07-10 13:07:59.147 INFO: 15 file-ids
[13592] 2010-07-10 13:07:59.147 INFO: checked branch file:///C:/PC1branchdir/ format Branch format 7
0.281 return code 0

However when I am on the cygwin bash shell or when I ssh to localhost (i.e. PC1), then this doesn't work:
bzr check /cygdrive/c/PC1branchdir/

This gives:
No working tree found at specified location.
No branch found at specified location.
No repository found at specified location.

The log file gives this:
0.062 bzr arguments: [u'check', u'/cygdrive/c/PC1branchdir/']
0.078 looking for plugins in C:/Documents and Settings/Administrator/Application Data/bazaar/2.0/plugins
0.078 looking for plugins in C:/Program Files (x86)/Bazaar/plugins
0.140 encoding stdout as osutils.get_user_encoding() 'cp1252'
[15072] 2010-07-10 13:08:37.772 ERROR: No working tree found at specified location.
[15072] 2010-07-10 13:08:37.772 ERROR: No branch found at specified location.
[15072] 2010-07-10 13:08:37.772 ERROR: No repository found at specified location.
0.156 return code 0

Does this have to do with parsing of the path I give? Can I check/change the way paths are beeing parsed?

The bzr+ssh problem is solved. I shouldn't have used /cygwin/c/PC1branchdir/ but just c:/PC1branchdir/. I was brainwashed by cygwin, sorry for that.

The file locking problem over SMB shares between OS-X and Windows still stands however. Since this is related to Bug #31006 and since I can manage with bzr+ssh, I'll mark this as solved. Thanks Gordon for your help.