Laptop Plugged Into Router, Now Wireless Connection Is Lost

I need the help of the collective braintrust here. This has me perplexed.
New Dell XPS 15 laptop. Out of the box working perfectly fine. Connected immediately to the wireless router, (Netgear WNDR 3700), and all was well.
I connected via a Cat5 cable the other night so I could transfer files from the old desktop I'll be junking. The desktop is connected to the router via Cat5. (Also have a second laptop on the network and the connection hasn't been affected by this problem at all.)
The problem is this: after transferring my files to the laptop I shut it down and disconnected the cable. When I turned the laptop back on a little later it would connect to the internet intermittently. Even when it did the connection was like molasses. Tried everything and every suggestion to fix the problem. Reinstalled the drivers, reset the modem and the router, uninstalled this and installed that. Finally, after nothing cured the issue, last night I formatted the drive and did a fresh install of Windows 7 Pro. Once I did that the connection was perfect again. Not knowing what I seem to know now I wired the laptop into the router and transferred my data. When it was finished I once again shut it off, unplugged the Cat5, and went on with things. Came back two hours later, turned the laptop back on, and once again I am unable to connect to the internet. Identical symptoms and the common cause seems to be wiring the laptop into the router.
What on earth is going on? Thank you for any help!

 

What wireless card is in your laptop. What driver version do you have for both wired and wireless and did you try the trouble shooter.

 

The card is the Intel Centrino Advanced 6230. Driver version 14.1.2.3.A04. It's the latest release from Dell, on August 17th.

 

The 6230 has been in numerous posts with problems. Many have not been resolved. I would query about it some to confirm. Other people will hopefully reply to this post. I am suggesting a different wireless card. The Intel 5300, 6200 and 6300 are the more trouble free cards they manufacture.

 

Not what I wanted to hear, but I will do some digging around to see if that is the cause of my problem. Appreciate the info. Thank you,

Here's the latest. . .
Spoke with Dell last night for about 45 minutes. He basically told me to uninstall and reinstall the network drivers. Been there, done that, it isn't the issue. He even suggested I flash the BIOS!
Here is my configuration if it helps:

XPS 15, L502X
i7-2630QM
6GB RAM
15.6 FHD B+RGLED TL
GT 525M 1GB Graphics Card
750GB 7200 RPM SATA Hard Drive
Backlit keyboard
Tray Load Blu-ray Disc BD-Combo (Reads BD and Writes to DVD/CD)
Intel© Centrino© Advanced-N 6230 & Bluetooth 3.0
90 WHr 9-cell Lithium Ion Primary Battery

The problem, as far as I can tell, is the Intel wireless card. Doing some research I found this thread: Intel Centrino Advanced-N 6230 won't...
Seems this specific card has been problematic, especially when matched with the Netgear WNDR3700 router, which is the model I have.
Trying to figure out my options here.
Replace the buggy card with another? If so, which card is recommended?
Call Dell again? But what will that do?
At this point my laptop is a desktop. I can wire it into the router and it runs fast and furious. But cut the umbilical cord and it's a paperweight.

Rant over. Thanks for listening.

 

There's of decent but not great wireless n half height mini pci-e cards out there. My Acer 4820TG has an Atheros AR9287 and it's actually been a pretty good card. Decent range, goes for <$15 on ebay etc.

 

This actually sounds like its an issue in the OS. The ethernet controller and the wireless controller are separate and there is nothing at the physical layer that would cause the wireless to crap out after connecting through ethernet. What OS are you running?

Here is what I would do.

1a. If you have that crappy Dell wireless utility installed, get rid of it.

1b. Make absolutely sure you have the most up to date drivers for both the wired NIC and wireless NIC. I even recommend trying a couple different combinations of drivers just in case it is one of the newer drivers that is causing the issue.

2. Prior to connecting to the router with ethernet, disable the wireless adapter to help prevent any problems that may occur at the logical link layer of the NIC.

3. After disconnecting from the router with ethernet, disable the ethernet NIC first, then enable your wireless NIC.

With Windows OS, if you connect a laptop with ethernet, Windows will override the wireless connection to prevent the IPv4 stack from pulling 2 IP addresses. This process is initiated and controlled within both the drivers for the NIC's, ethernet and wireless, and within Windows WLAN Autoconfig Service and Wired Autoconfig Service. Both those services have underlying services that they rely on, including the drivers for the NIC's and if any of those services are not communicating properly you are going to have problems.

 

Appreciate the replies and information. Thank you.
What I found in the past few days is that in Windows 7 Pro, in the Power Options, there is a menu that includes options for the Wireless card. Apparently, by default that sets itself to a save power mode when the laptop is running on battery power. I switched that to the Maximum Performance mode and the problem has been resolved and the laptop has been fine since.