Ubuntu 9.04 write problems with Network Accessible Storage Device

[Duffields]

I have been using a DNS-323 NAS device for the data files on my home network 
for the past 3 years with no problem.  Each computer mounts the device 
through an entry in fstab shown below

//192.168.0.49/Volume_1 /media/RAID cifs 
credentials=/home/xxxx/.smbcredentials,uid=xxxx,gid=users 0 0

The system has been working very well with Ubuntu 7.10 and 8.04.

I have started to play with Ubuntu 9.04 and I find that although I use the 
same entries in fstab as with 8.04, and the drive mounts correctly, many of 
the files, (perhaps all of them, but I have not checked them all) can be 
opened as "read only".  Changes to images cannot be saved nor can changes to 
documents.

The odd thing is that some documents such as NoteCase Pro .ncd files CAN be 
saved by that application.  Also, I can add new directories and put files 
into them but then cannot edit those files.

Has anyone encountered this?

Mac