Personal file sharing: file copying broken from/to imported account?

Question

I have an iMac G5 with two user accounts A and B ; and a MacBook Pro with two user accounts A' (imported from A with the migration assistant) and C.
Personal file sharing, FTP and SMB are enabled on both machines. The firewall is disabled. Permissions, as well as the Keychain have been repaired.
When I am logged as A' on the MBP, and when I connect to the iMac with the username/password of A, I can't copy files from A' to A : I get the following error message [The operation cannot be completed because you do not have sufficient privileges for some of the items]. However, a 0-byte file is created on A'. The same problem occurs from A to A'.
This problem drives me crazy because :
- I can read and delete any file in A' from A (and vice-versa). Only copy and modification doesn't work.
- I can copy files from A to C, A' to B, C to A, B to A'.
- FTP sharing between A and A' does work.
Someone got the problem solved by re-creating his account and re-importing all his data, but I absolutely want to avoid that. I'm sure there can be a simpler solution...
It appeared to me that the only reason why AFP copy doesn't work between A and A' is that A' was imported from A. It seems also that a common broken preference/setting is not the source of the problem, since sharing works from/to any other account (and well, re-creating the account couldn't solve the problem as it would re-set the broken settings).
I would like to know which information is used to determine user privileges when copying from one machine to another...
A strange thing I noticed is that both A and A' have the same generateduid (which is thus not "unique") - could it be the source of the problem?
If you have two machines with one account imported from one machine to another, can you check whether Personal file sharing with this account works? I love understanding why stuff doesn't work.
Thanks!

Answer 1

Here are the results of a few more experiments... Something is definitely broken with those two user accounts, but I'd like to know why, and how it got broken
I have replaced the names of the accounts/machines by more meaningful identifiers.
From the MBP, trying to access Account_B on the iMac:
MBP:~ account_A'$ mkdir test
MBP:~ account_A'$ mount -t afp afp://accountB:*****@iMac/accountB test
mount_afp: the mount flags are 0000 the altflags are 0020
MBP:~ account_A'$ ls -l test
total 0
drwx------ 29 account_A' account_A' 942 Nov 8 22:28 Desktop
drwx------ 14 account_A' account_A' 432 Sep 24 23:47 Documents
(And I can copy whatever I want in test)
Now trying to access Account_A:
MBP:~ account_A'$ mkdir test
MBP:~ account_A'$ mount -t afp afp://accountA:*****@iMac/accountA test
mount_afp: the mount flags are 0000 the altflags are 0020
MBP:~ account_A'$ ls -l test
total 0
drwxr-xr-x 23 501 501 738 Aug 26 00:03 Code
drwx------ 13 501 501 398 Nov 8 13:10 Desktop
(I can't copy to test here)
501 is the uid of account_A (on the iMac). (The uid of account_A' is 503).
Same stuff through SMB:
MBP:~ account_A'$ mkdir test
MBP:~ account_A'$ mount -t smbfs //accountA@iMac/accountA test
Password:
MBP:~ account_A'$ ls -l test
total 0
drwxr-xr-x 1 account_A' account_A' 16384 Aug 26 01:03 Code
drwxr-xr-x 1 account_A' account_A' 16384 Nov 8 13:10 Desktop
(In this case, it works)