I have no idea as to whether this is applicable or not, but I found this after doing a bit of hunting.
Quote:
Troubleshooting Tips
Verify that you have called your cable service provider and given them the serial number and MAC address of your cable modem.

Source: http://www1.cisco.com/web/consumer/support/modem_DPC2325.html#~troubleshooting

Additional searching also brought me to this which sounds like it might be applicable.

In any case, this is a problem/situation with your router/modem and/or ISP, not mIRC.