Erratic cable modem behavior

I have a Toshiba PCX1100U that a couple of months ago started acting weird. Usually it works but lately I will try to go to surf the net and my cable connection will go out. After 30 seconds or so the cable light will blink rapidly and then stay on at which point data transfer resumes. I just built a new rig and the same thing happens so it appears it's the modem. I always have an internet connection, its just the data transfer that stops. Do I need to buy a new modem or is this something that I can resolve? If I need a new modem anybody know of any good reviews or have any specific recommendations? Thanks a lot.

Yes I do have a router, but the modem is "upstream" from the router and the modem and router have been functioning together for months now. I bought this modem from a cable company when I lived in another state, so I don't think any lease applies. You think it is not a hardware problem?

Ok I found the lease time under DHCP Server tab. I didn't see anything about lease time in either WAN or LAN. Under the DHCP Server tab, the DHCP Server is enables, and then their is the starting and ending IP addresses which I dictated (yes my IP address is in this range), then their is a drop down menu for Lease Time which varies from 1 hour to 1 week. By default it is on 1 week. Static DHCP is disabled. Then my name is listed as a client with my IP address, MAC address, and Expired Time which is on the 18th of August 2006 at some time. So what should I change?

I had a choice of 1,2,3 hours or 1 day so I picked 1 day to see if it helped and I've been surfing for 30 minutes without interruption and I would of had multiple interruptions by now. I looked on D-link's site for advice and it didn't say anything about lease time when configuring modems. The only thing it said to do that I hadn't done already was clone the MAC address, but since it seems to be working I won't worry about it. Also, I noticed my firmware is out of date so I will update it soon. Thanks for your help!

Well the log options I have is for system activity, debug information, attacks, dropped packets, and notice.
Right now system activity, attacks, and notice are checked.
I don't think I'll change it since I have been in the clear so far, but if it changes I will cut that down and see what happens. Thanks for the help I really appreciate it.

well sure enough when I updated the firmware, now the damn thing doesn't work. It looks like the WAN setting are nonexistent. I made sure that it was dynamic IP and put in the default DNS server but when I check the status it says DHCP client disconnected, the IP adddress Subnet amd DNS are all 0.0.0.0, and when I click on renew DHCP server it just times out. Another weird thing is the clock is stuck on 2002 unless I switch it to manual but that doesn't really change anything. what did I do? Should I try to get the old firmware and upload it or reset to default factory settings. Right now connected straight to my modem.

Well when I shut everything down and unplugged everything for a couple minutes and then plugged the modem and then the router in, it worked when I powered up the computer. Apparently what happened was the older modem I had wasn't able to synchronize with the router and caused the WAN port to go crazy. It's important to let the modem stabilize the data stream before plugging in the router. Thanks for your help again.