Samba share-security strangeness

[jcman]

I have a Redhat 9 box set up with Samba, and want to share out a few data CDs, so don't need any authentication. This should be simple, right? Well, it works, at first. But, once a Win2k or WinXP user has gone to another program or two, and then wants to access one of the CD images, he can't find the CD, or is being asked for a password for the guest account. ?!? Once they log out and then back in, if they FIRST go to the CD, they can get in just fine. Otherwise, they repeat the no-find or login fun. Below is my stripped-down smb.conf. Ideas?

#======================= Global Settings =====================================
[global]

workgroup = YADA
netbios name = Yada_yada
server string = Yada_yada
hosts allow = 192.168.168. 127.
guest account = pcguest
log file = /var/log/samba/%m.log
max log size = 0
security = SHARE
socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
remote browse sync = 192.168.168.1
remote announce = 192.168.168.255
local master = no
os level = 3
domain master = no
preferred master = no
wins server = 192.168.168.1
map to guest = baduser
#============================ Share Definitions ==============================
[homes]
comment = Home Directories
browseable = no
writeable = yes
valid users = %S
create mode = 0664
directory mode = 0775

[tmp]
comment = Test file space
path = /tmp
readonly = no
public = yes

[02forms]
path = /mnt/isosvr/02forms
comment = 02forms
public = yes

[tmfc]
path = /mnt/isosvr/tmfc
comment = tmfc
public = yes

...etc...

TIA