NE2000 ISA + bus mastering...

I've a problem, I'm missing bus mastering on one of my NICs. I assume this because the CPU load is constantly around 100% (kernel times) when I transfer data through this network card. I know there exists bus mastering of some kind for my configuration since I had it before I reinstalled my system. Now I have the following configuration:

[internet]--[NIC1 (WinXP Pro ICS) NIC2]--[LAN]

NIC1 works as it should (PCI PNP etc), but it's NIC2 that I want to "fix". The computer (that also functions as a router in this case using ICS (Internet Connection Sharing), is running Windows XP Pro. The computer's configuration (as applicable to this problem) is:

Motherboard ABit KT7A-RAID v1.1
- (WCPUID) Host bridge: VIA Apollo KT133
- (WCPUID) ISA bridge: VIA VT82C686B
- Driver: VIA Hyperion 4.45, USB Filter 1.10 (amongst other)

NIC2: NE2000 compatible 10-BASE-T (ISA) (is connected on the "ISA bridge" as I've understood)
Device Manager: "NE2000 Compatible ISAPNP Ethernet Adapter(Generic)"
Driver: \System32\DRIVERS\ne2000.sys
Provider: Microsoft Corporation
File version: 5.1.2600.0 (XPClient.010817-1148)
Copyright: (...)
Digital Signer: (signed)

I'm grateful for any hints to which will lead me to a solution to my problem.

Thanks in advance!