samba - Jun 2008 - Mapped share looses write/user permission on inactivity -- how to avoid

Hi

I have set up a solaris 10 with sfw and presented a share to the clients.
Anonymous access should result in read permissions. The "edicom" user
should have write permissions as well. This works. Trusted clients map the share
to some windows drive and can write to the share.

... That is until some time has passed. Then they get permission denied when
trying to write.
Is that the expected behaviour with the config below? And how do I stop it from
happening?

workgroup = WORKGROUP
server string = Sol10u4 CIFS Server
log file = /var/adm/samba_log.%m
security = SHARE
load printers = no
disable spoolss = yes

[edi]
comment = EDI data
path = /export/home/edicom/data
browsable = Yes
read only = no
valid users = thosan edicom guest nobody
read list = thosan, guest, nobody, edicom
write list = thosan, edicom
guest ok = Yes

-- 
Thomas