I'm running on a Lenovo W520 with Windows 7 Pro SP1, Intel Centrino Ultimate-N 6300 wireless adapter with the latest drivers from Intel (newer than those from Lenovo.) Since I took this machine out of the box new in January, I've had issues with slow network connectivity. I monitored the network connection and noticed that it would 'hiccup' randomly while I was saving a file to a network server or trying to print. I changed from letting Windows manage the adapter to using the Lenovo Access Connections manage the adapter. With that utility, a sound is played when the network connection hiccups - which happens a lot more often that I thought - still random - but at times every minute or so. After three months of searching for a solution here and elsewhere, I was tired of fighting the problem and called Lenovo support. They insisted it was a NIC issue. I sent it in for a swap out. I just received the unit back. Within 5 minutes of booting it up, the problem happened. FYI - I have four XP machines running on my wireless network that never have a problem. When the hiccup happens, I rarely lose my internet connection - aka - I don't notice an issue while browsing. Where it does affect me is when saving files to the network server. Nearly everytime I get a "Not Responding" error. Rarely have I been able to print anything of size as the hiccup interrupts the print job. I can print the same file from an XP machine without any issues. If I direct connect to the printer, the job prints OK. For me, all problems point to the OS. Today, I'm trying to work from home and am remoted in to my office computer. The hiccups are happening "as usual" but effecting my remote session, causing noticeable slowdowns, although the connection has never dropped. The sound from the Lenovo Access Connections is annoying enough though, I took a break to see if the event logs would tell me anything. Lo and behold - in the MS Windows DHCP Client Event/Admin I see an informational message when the connection hiccups: Dhcp has received network hint 777716E637F607 for the Network Card with the network address 0x2477031E688C which is followed within 3 seconds by an error: The IP address lease 192.168.1.140 for the Network Card with network address 0x2477031E688C has been denied by the DHCP server 192.168.1.1 (The DHCP Server sent a DHCPNACK message). I changed the TCP/IP settings on the adapter from using DHCP to a static address and not a single hiccup since. No slowdown on my remote connection and I just printed a 257 MB graphic without issue. Any ideas what is going on?

It looks like that your DHCP server (or router) is denying request for a new IP address. The computer seems to be sending request for a new IP address and DHCP is refusing to issue one. When you use static IP address you are not affected by this. One thing you can try to do is to increase the lease time on your dhcp server for IP addresses.

I'm using a Netgear router with a defalut lease of 24 hours. I don't believe there is a way to change the lease time. I didn't go into everything I've tried to resolve this, but one of the items was to power down everything, then bring up the router first, then power on the wireless peripherals. Withing 5 minutes of the Win7 machine getting it's lease, I started having the hiccups. I wasn't monitoring the DHCP Client Event logs at the time. To confirm, I will do the power off again, only this time monitor the event log after reconnecting. The computer shouldn't even be attempting to get a lease for a least 12 hours if I remember my DHCP protocol correctly. And if it was a DHCP server issue, why don't I see it on any of the other (non Win7) machines?

Please see this forum thread this seems to be very close to your problem http://social.technet.microsoft.com/Forums/en-US/w7itpronetworking/thread/52a59bd5-c4d9-42c1-8124-5c8e4eb11fe4/

I have a similar issue and I agree with wwansop that it is not a DHCP server issue. The question linked in the currently accepted answer is unrelated. If anyone can lend further assistance, it will be greatly appreciated.