Funny, I had exactly the same issue with my NIC 3c509B. On my 486 it would prevent WfW3.11 from loading, and in Windows 95 would crash when I hit the 'Test' button. I just moved it to my Pentium (socket 7) machine, and WfW3.11 now loads but the NIC doesn't work, and in Windows 95 it still hard crashes when I hit test. Fortunately, it works in Windows 95 otherwise! Maybe it's not your system as I had the same trouble..

Try an Intel or some ne2000 clone.

Try the crynwyr packet driver for these cards.
http://crynwr.com/drivers/

Brickpad wrote:

However...
Both cards prevent Windows for Workgroups from loading (hangs at the splash screen) after I install the drivers, or use the driver that comes with Windows. I've already looked for possible IRQ and DMA conflicts. There aren't.

According to my experience (from past and from retro computing), Windows for Workgroups will not start If your NIC is not connected to a network, it will just hangs at the logo screen.

tayyare wrote:

According to my experience (from past and from retro computing), Windows for Workgroups will not start If your NIC is not connected to a network, it will just hangs at the logo screen.

Funny you should say that, but that is exactly what I was thinking as well. I have it set up for DHCP, but I haven't connected it to the switch just yet. I'll give that a shot later and see if that solves the problem.

bjt wrote:

Try the crynwyr packet driver for these cards.
http://crynwr.com/drivers/

Thanks, but I don't know what exactly what I'm looking for?

3c509116.zip which contains a v1.16 packet driver from 2002.

You have a more serious resource allocation issue on this system, nevertheless.
If the 3com card can correctly update and store its configuration data "once upon a boot time" but not next time, you might have another device at the same port address. I would re-Check with a bare bone system, using a different multi I/O card.

Jolaes76 wrote:

3c509116.zip which contains a v1.16 packet driver from 2002.

You have a more serious resource allocation issue on this system, nevertheless.
If the 3com card can correctly update and store its configuration data "once upon a boot time" but not next time, you might have another device at the same port address. I would re-Check with a bare bone system, using a different multi I/O card.

Thank you. I thought it might have been a resource conflict as well, but I checked all available IRQs and addresses via MSD and nothing was conflicting. I had to bypass MS-DOS startup files to test / configure the card.

[UPDATE]
Everything seems to be working fine now. I was able to boot in WFW once I was connected to the switch, and share file folder over the network.

So, I had this exact same problem of computer hanging or crashing when using the provided 3Com drivers, and this post got me in the right direction, although the actual solution is never stated anywhere.

In my case I was running the auto-config option of the 3com setup program when trying to set up the resource parameters, and it always said it saved the new values to the card, but clearly it didn't since running the crynwyr packet driver would show different resources from the ones supposedly set by auto-config, while running the official packet driver would just hang. Jolaes76 was right in regards to there being a resource allocation issue.

The key to solving the issue was turning off "plug & play" in the 3Com config program, rebooting and then setting the resources automatically again. This time they were actually saved to the card and there were definitely no conflicts.