> Your problem is really baffling.
> Recreating /etc/passwd should have no negative effect,
> and editing the uid in /etc/passwd should not matter.
> 
> - Are there perhaps two FischRon on the machine, a domain
> user and a local user?

No, but could it be that there is a problem with upper/lowercase?
My Windows login is "fischron" (all lower case), but when I send
email, the address is "FischRon.external@infineon.com". Of course
spelling does not matter in email, but maybe this is a hint that
my user id is written in different case on two different places,
where it really should have been written in the same way?

> - Could you send me the outputs of "cacls x" and "cacls y",
> where x and y are the files you ran getfacl on?
> - Also run "strace -o trace.txt chmod 660 x" and send me 
> trace .txt.

Actually, the permission problem was identified to be wrong Windows
properties (see my related posting under the heading "ssh ceased 
to work after recreation of /etc/passwd"), and after I manually
changed these permissions for file x, it now behaves fine. However
I include here the cacls output for another file where I did not
correct the Windows file properties yet - maybe you can see extract
additional useful information from it:

~/tmp $ cacls tg.pl
h:\tmp\tg.pl EU\fischron:C
             EU\MUC-ADM-FileOperators-Home-L:C
             VORDEFINIERT\Administrators:F
             EU\MUC-ADM-FileOperators-L:F

Here in contrast a file which works:

~/tmp $ cacls y
h:\tmp\y EU\fischron:(Beschr"nkter Zugriff:)
                     STANDARD_RIGHTS_ALL
                     DELETE
                     READ_CONTROL
                     WRITE_DAC
                     WRITE_OWNER
                     SYNCHRONIZE
                     STANDARD_RIGHTS_REQUIRED
                     FILE_GENERIC_READ
                     FILE_GENERIC_WRITE
                     FILE_READ_DATA
                     FILE_WRITE_DATA
                     FILE_APPEND_DATA
                     FILE_READ_EA
                     FILE_WRITE_EA
                     FILE_READ_ATTRIBUTES
                     FILE_WRITE_ATTRIBUTES

         EU\Domain Users:(Beschr"nkter Zugriff:)
                         READ_CONTROL
                         SYNCHRONIZE
                         FILE_GENERIC_READ
                         FILE_GENERIC_WRITE
                         FILE_READ_DATA
                         FILE_WRITE_DATA
                         FILE_APPEND_DATA
                         FILE_READ_EA
                         FILE_WRITE_EA
                         FILE_READ_ATTRIBUTES
                         FILE_WRITE_ATTRIBUTES

         Jeder:(Beschr"nkter Zugriff:)
               READ_CONTROL
               FILE_READ_EA
               FILE_READ_ATTRIBUTES

I have also attached the trace.txt of 

  strace -o trace.txt chmod 660 tg.pl

Ronald