Ghosted(replicated)drives on NT4 Network

Some of our users experience doubling up of network drives on an intermittent basis.
e.g. H:\\user\fred_bloggs
I:\\user\fred_bloggs
J:\\user\fred_bloggs
etc

We think it may be the switches(3Com 3300),
we have tried forcing full duplex, 100 on both netcard and switch.
Up to Service Pack 6.0a on server and pc.
Any ideas appreciated.