Why Do I Get DISCON'd from IRC every 20 minutes?

I haven't changed anything on my set up, but I'm getting temporary losses of connection (which knocks me off IRC, and then my PC doesn't realize this, so I don't get my discon message hours later when I try to type)

Is there a common reason for this somehow or is it more likely ISP related?

I had this problem ~1.5 years ago.

Are you just seeing all the chat messages in all the rooms stop, and then when you come back, try to type something you get a 10054 Software abort/Connection reset by peer error?

My problem was due to a faulty NIC mis-handling TCP checksums... it was also causing my AIM to sign on/off randomly. Only way I caught it was using Ethereal to sniff the IRC packets (for Ping? Pong) and AIM packets and I found out what was going on.

When I had my net work set to DCHP and the ips were being distributed whenever someone logged on, I had the same trouble.
I had set port access based on a static configuration, ie set specific ports to specific ips.
Depending on who logged on first, it would work or not.