Windows explorer slow, or hangs, when manipulating shared files

I have 'file and printer sharing between two computers using a router (though
had same problem using ICS), running WinME. When viewing files on the other
computer with explorer, at first everything is fine, but after I have moved a
file across the network explorer becomes very flakey, first freezing,
starting again and eventually freezing up. I have one wired connection to the
router and one wireless, but previously had identical symptoms with a fuly
wired daisy chain co-ax connection. The wired card is a Realtek 8029(AS) and
the wired one a KCorp KLG-530. I have searche KB but cannot find anything on
this. The wired computer is running Zone Alarm Pro with the local net set to
'trusted'.

Thanks for any help.
Phil