Error 55 when using net use

Hello,

I have a Win98 machine (several of them actually), which have problems
connecting to a WinXP Home PC using the Windows Networking. All
machines have TCP/IP protocol installed as well as Novell Netware IPX/
SPX stack. When I try to map a share from the Win98 box to a WinXP
box, using syntax like:

net use e: \\WINXP1\DRIVEC

I get the following error:

Error 55: The specified resource is not available. The computer that
shared the resource might have been turned off , or the permissions
might have been changed. For more information, contact your network
administrator.

I have file sharing turned on the WinXP box, with full read/write
priviledges. What is odd is that I can map to another WinXP home
machine from this Win98 machine. The workgroups are the same, and I
can ping the machines from each other. No firewalls are installed on
the WinXP boxes.

What am I missing here?
Thanks.
Mike