samba - Oct 2013 - Windows XP client apps crash/hang when starting file-picker

Hello.

I have a small and simple local network with a Samba server (v.3.6.6 on 
Debian Wheezy) and Windows clients, a mix of Windows 2000 and XP 
(32-bit) and 7 (64-bit). In recent times, possibly since I upgraded the 
server OS version, but most likely before, the Windows XP clients (but 
not 2000 or 7) have all experienced problems where if any application 
tries to open a file-picker (for either opening or saving a file) where 
the default location (i.e. the directory the file-picker starts with) is 
a drive letter mapped to a Samba share, the application either hangs or 
crashes. However, starting with a direct Samba share, or a local drive 
letter, works fine. The problem happens every time, with any 
application. The clients are all fully patched, and have no realtime 
antivirus or any other strange stuff that I know of. Samba log level 3 
shows nothing obvious (to me).

My smb.conf is shown below (apart from the ordinary shares, and some 
names have been changed).

If anybody can shine some light on this, it would be much appreciated.

Thanks a lot.

Tony


smb.conf:

##### GENERAL #####

[global]
map archive = no
time server = yes
enable privileges = yes
passdb backend = smbpasswd
#log level = 3

# the following line seems to make no difference either way
#socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192

##### DOMAIN #####

domain logons = yes
domain master = yes
logon drive = H:
local master = yes
logon path = \\%L\%u\windows
logon script = netlogon.bat
preferred master = yes
os level = 255
security = user
server string = Debian GNU/Linux with Samba 3.0
workgroup = MYDOMAINNAME

##### PASSWORDS #####

encrypt passwords = true
unix password sync = yes
passwd program = /usr/bin/passwd %u
passwd chat = *New*UNIX*password* %n\n *ReType*new*UNIX*password* %n\n 
*passwd:*all*authentication*tokens*updated*successfully*
pam password change = yes
check password script = /opt/mysoftware/testpw

##### PRINTING #####

printing = cups
printcap name = cups
load printers = yes

[printers]
path = /var/spool/samba
public = yes
printable = yes
guest ok = yes
read only = no

[print$]
path = /var/lib/samba/printers
browsable = yes
write list = root

##### SHARES #####

[homes]
browsable = no
inherit permissions = yes
preexec = /opt/mysoftware/onlogin %U
root preexec = /opt/mysoftware/onlogin-root %U
read only = no
csc policy = disable

[NETLOGON]
path = /opt/mysoftware
browsable = yes

[profiles]
profile acls = yes
path = /home
browsable = no
read only = no
create mask = 0600
directory mask = 0700

[mysoftware-files]
path = /var/mysoftware
read only = no
inherit permissions = yes
browsable = yes