Can't Access NAS

For some strange reason I've been unable to access My NAS drive since I
swapped my XP laptop for a Vista Business one.

If I try to access any files on the NAS then the Windows Explorer (or file
selector dialog) just hangs with a 'Not responding' error message.

I have fiddled with the NTLM settings in the group policy editor to use
older versions of NTLM and this has allowed me to progress from not even
being able to access the drive at all to now being able to view files on the
root directory of the drive but not navigate deeper or open up any of those
files.

The NAS is a Maplin branded enclosure containing a self-installed 200gb IDE
drive, there appears to be no later firmware availalbe than the one I have.

AN interesting point to note is that I use the Ultra-Edit / Ultra-Studio
suite of programs for web page development, and this has it's own 'Tree view'
in a pane on the left hand side of the screen, if I use this pane to select
files I can open them in Ultra-Edit as this by passes the Windows File
Selector dialog. But if I use the Windows File Selector in Ultra-Edit then I
get the same crash.

Seems like a glitch or setting setting change required in Vista if you ask
me, but I don't know where to go from here.

Any suggestions greatly appreciated.

Neil