XPS 8300 brand new connects to the Broadcom Netlink Communication card only after rebooting 3-4 times at cold-start.

@arborlinden: I think that's the correct driver.  You can download it from broadcom's website.  I did that, and installed the new driver, but it didn't fix the problem.

Now if we can get Dell to reimburse us...

I have the same computer and same problem. I have uninstalled and reinstalled the drivers several times and problem keeps recurring whenever the computer enters the sleep mode.  Restarting usually works to reconnect the Broadcom Netlink wired adapter.  Tonight I went into device manager and when I right clicked on Network Adapters and clicked "Scan for hardware changes" the Broadcom adapter reappeared and reconnected.  I have removed the check mark from "Allow the computer to turn off this device to save power", but that hasn't made any difference.  Hopefully, if enough of us complain, Dell will take the time to figure out a solution.  I also have an "unknown USB device" that Windows stops with error code 43.  If I uninstall the unknown device it just reinstalls and Windows stops it again.  I have no idea what device is involved since everything connected works, but thought I would mention the issue in case there may be some relationship.

Dell, are you listening?

I already post a lot about this issue. I still have warranty so I will let them replace the motherboard today they will come to pick it up.
If this would not solve the problem I will straight away ask my money back & I m happy that you think the same too.
PS
the first day i received my pc I have seen that there are two network cards one plugged & the other one unplugged & i said to myself as long that it works it won't be a problem but now it's time to go to the point.
I'm still thinking that is an assembling problem. Dell already knew what is going to happend to the XPS 8300 i m almost certain they they did. they had also problems with optiplex & they sold it to customers so it won't be the 1st time for them.
I will let know after 10 working days.

Motherboard being replaced today. I'll post an updated status later.

Use search to find driver k57nd60a. Then fire up run regedit and search for k57nd60a. On my system registry was telling system to look for file where it wasn't so I copied file to directory specified in registry. Only had time to do a few reboots but now driver is being loaded as soon as it windlows starts looking (no little circle over network icon) Hope this makes sense. Looks like windows was looking in srong place for driver and sometimes found it by pure chance and sometimes not. Hope this is not steering you fellows wrong but worth a try. Please let me know if it works for you

New motherboard is in and I'm up and running. Cold booted first time and I've rebooted a couple of times since with no issue.

I'll monitor for a couple of days and post an update.

Thanks for the idea arborlinden.  My driver is located in the correct location (c:\windows\system32\drivers) pointed to by a few registry entries.  

As for cold booting from my Linux thumb drive, the last two times it hasn't found the NIC either.

Looking forward to your feedback FrenchPete - if the new motherboard provided a fix.

By the way...I think the conclusive evidence came from launching Diagnostics to check the hardware functionality of the system:

1. Reboot the system.

2. Tap seven -eight times on the keyboard when the Dell logo appears.

3. We will get the boot menu.  Select Boot to Utility partition and press ).

4.Choose option "TEST SYSTEM, Else choose option Custom Test from the options

5. Please locate "Network Adapter", click on that. Start test, by clicking on the start test button.

When I tried this - there was no Network Adapter found from a cold boot.

suggest you copy file to system32 anyway

FrenchPete,

A quick question, when you had the motherboard replaced, did you have to reinstall all your software, or was it as easy as replacing the motherboard, plug system back in and you were up and running?  Also, when I think back to when my system first started with this issue, my computer went into "sleep" mode, and when I woke it up, no network card showing?  So you may want to put it in sleep mode a few time to test also.

I'm just one of many looks like that have been experiencing these same intermittent issues with the NIC on my Dell XPS 8300. These past few months have been a nightmare for me with Dell. And I too believe this will be my last Dell. Where my situation gets even better is that this Dell XPS 8300 was actually my replacement for a Dell Studio 540, a 2 1/2 year old system, that one day decided not to turn on. Spent the entire month dealing with Dell tech support, an unresponsive supervisor, a Dell tech support agent getting sent to my house with a box of parts twice. Replacing about every piece inside that thing, with no luck. That's ok, thanks to my warranty I get this nice new upgraded Dell XPS 8300. And well here we are today. What else can I say? I am in shock. I am disgusted. Do I want to deal with tech support again, or just buy the $20 external card? The later may be the way choose to go.

I tried doing what you suggested but could not figure out what you did.  I ran regedit and found the driver in HKEY_LOCAL_MACHINE, Microsoft, Windows, Setup, PnpLockdownFiles.  Like Ralph, I also found the driver in the same location noted in his post.  I have no idea what to do from there and would need much more specific instructions.  I am also concerned about messing with the registry.

Too bad the wizards at Dell don't monitor these postings and provide the answers.

So far so good, it seems to be coming out of sleep fine now. Replacement was a doddle - took about 30mins with no issue. The guy was an authorised specialist (ran his own business) so knew his stuff.