System hang on Open/Save From/To Server

I tried posting this under autocad 2002 but it was suggested that it might be better here, so here goes...

I work in a small computer store with a great many customers, some of
which use AutoCAD.

One of them in particular is having a specific problem that I have been
having some problems diagnosing. I have a suspicion of what the problem
might be and am looking for confirmation or a different diagnosis...

The problem is as follows.

- They are a land Survey Company and have 7 computers in the office all
using various versions of autoCAD.
- All their files are stored on a new file server that I put together
using Windows XP Pro
- The people that are having a problem are mainly Windows 98 Machines
using AutoCAD 2002 (Not the Network enabled version)
- What happens is when they attempt to Load or save a file from the
server the system occasionally hangs, requiring a re-boot of that system
and sometimes the server itself
- They can copy files to and from the server without an issue using
normal windows explorer copy and paste techniques, it's just when they
use AutoCAD to access the server, a problem happens.
- Also, they say that it sometimes seems to be fine with only one or two
people accessing files, the problem happens most often when they try to
go above that.
- I've tried put in different Network card, they are running a 10/100
Switched HUB.

Frankly, I'm at a loss. Recently I Ran across another Tech who
described a similar, although not exactly the same set of symptoms and
when the company upgraded to a network enabled version of AutoCAD, the
problem was cured. Is this what they need to do?

Any help in this would be greatly appreciated.

Thanks in advance.