lost net and email services

[nork]

have it back now but:

Internet and email were fine when i went to bed, when i got up in the morning, no internet or email, the last email was received at 3:40 am.
My bill was paid up to date, i checked with my isp and they said there was no general probs in my area(which does happen sometimes), and they tried to help me but in the end said that pinging showed that the problems were on my end.
I did have a network setup for my cable modem, but because my isp tech support will only help if you are not on a network, i simply changed to simple cable modem setup with no network.
I disabled my onboard lan (Sis 900) and installed a pci nic card and I am up and running again in win98se.
When I first uninstalled my onboard nic drivers i got an error message, windows protection fault and couldnt even get into windows but that is another story.I got around that.

My next step will be to disable my current pci nic and re-enable my onboard lan and see if it will work.
I did add a knm switch, cables for switch, and another computer to my setup. That was running for 2 weeks before i lost my net and email. Could this have anything to do with the problem?

Now that you have the background what I would like to know is:

Is it common for onboard nic setups to just die like that?
Are there inherent probs with onboard sis900 chipsets?
I hadnt installed any other programs in the last month or so, so that is not the prob. Although norton av probably updated itself i dont let any other prog, incl windows update itself, only norton av. The rest i do manually or not at all.

Thanks for any consideration.
Also, since I am a lowly member here i dont get email notification that i have received a reply so it may take a bit of time for me to answer any questions you may pose.