HP1000r VLANs Low bandwidth utilization

[V. Smirnov]

Hi,
OK, that's what we have.
fact:
HP Netserver LP 1000r(1.13) / HP 10/100TX NIC (integrated)
NW4.2(sp9)/2VLAN/3COM SuperStackII 3300 switch/IPX+IP
Workstation: Win98SE/NWClient 3.32
symptom:
Extremely low bandwidth utilization with both VLAN connections active,
when copying a large number relatively small files, lets say WIN98 directory.
As soon as one of the VLAN disconnected from the 3Com switch,
(just the patch cable is pulled out), the bandwidth utilization changes to normal.

When copying a large file, lets say HDD clone (300Mb) the bandwidth utilization normal
(more or less).

Nothing helps to lift the bandwidth on the port of W98SE up.
Any idea?
TIA
Val