I have HP tx2514ca with Broadcom wireless mini-pci adapter and D-Link DIR-625 router. Since installing Window s7 64bit Im having problems connecting to my Wi-Fi router if my adapter is set to DHCP, it will sometimes obtain IP address but most of the time it will not. If I set the IP address manually it will work all the time. I tired drives that came with Windows and HP ones the same problem. This worked all fine under Vista.

As it worked fine with Vista I'm wondering if the "network hints" are the bad guy in Windows 7. Try and turning it off according to http://blogs.technet.com/teamdhcp/archive/2008/12/19/how-to-configure-dhcp-network-hint.aspxto see if that improves you situation.

Well I tested it over few weeks now and the above did not solve the issue, have to have manual IP address or DHCP will mostly not work. Even setting manual IP will not always get me connected now, I noticed that I will get best chances of successful connection by restarting laptops, coming out of sleep or hibernation will often cause problem with Wi-Fi connection. I have Dell & HP laptops running Windows 7 with Broadcom & Intel chipset wireless adapters and they have the same issues. I have Lenovo laptop running Windows XP and it connects to the router without any issues, re-start sleep hibernation all ok. I wonder if this problem was caused by some kind of Windows update as initially Windows 7 installation worked ok, problem started first with HP laptop then with Dell.

I purchased new N route as a test and problem went away. However I’m still baffled why this happened as XP client had no problems with connecting as well as my XBOX 360 and PS3 only Windows 7 clients.