Wireless not working

[GreyGeek]

Are any of those "other machines" a Linux box? Either way, if Windows connects then Kubuntu should connect. My experience with a faulty connection on this laptop occurred when I upgraded my previous installation, the 12.04. The new kernel (ath9k.ko) driver didn't work properly, and my wireless was constantly throttling up and down, but most of the time would hang at 1Mb/s or disconnect. When I tried a kernel release greater than 3.8.x (i.e. 3.9) functionality was restored.

[Don]

All of the machines have identical configurations, within the limitations of their hardware. All are running Kubuntu 14.04 with Windows 7 vms. I may have been unclear about what's working and what's not. On the "trouble" machine, when network connectivity is out, it is out both on 14.04 and on the vm; I have not seen a situation where one will connect and the other won't.

I just rebooted that machine. Before the reboot, no network connection, wired or unwired. After the reboot, 14.04 connected (wired) with no problem. Then I tried to boot the 7 vm, but I got a VMware unrecoverable error: Unexpected signal: 11. There is a log file, which means nothing to me and is too long to reproduce here. I tried to attach it as a text file, but the system told me I am a bad person and would not accept it. Perhaps it is moot anyway, since I did get the vm started..

While I was typing this, BTW, the trouble machine lost connectivity. I rebooted; then it had it back again. Then I tried booting the vm into safe mode with networking; that worked. Then I rebooted the vm with a normal startup. That worked with no error message, and I had wired connectivity. Still no wireless.

It's about 2:45 where I am. I'm going to leave that machine alone (totally--no movement, no keys, no mouse) except for trying to get online every fifteen minutes or so. At some point I expect it not connect. I'll let you know.

[Don]

3:06 p.m. Getting weirder still. Wired connectivity on the vm; none on Linux. I've jumped back and forth several times from one machine to the other; the pattern persists. I wonder whether rolling back to 12.10 makes sense. It's not that hard to do, and I have backed up all my data and the vm.

[Don]

4:09 p.m. Same as an hour ago: yes on Windows vm, no on Linux.

4:11 p.m. Rebooted Linux: connected to internet.

4:13 p.m. Rebooted Windows vm (yeah, rebooting Windows takes a while): connected to Internet.

4:14 p.m. Went back on the Linux machine, without rebooting: Still connected.

I'm contemplating going back to punch cards.

[GreyGeek]

Those are weird observations indeed! That your other machines, also Kubuntu driven, work fine, suggests that the fault is with the problem machine. While you have given all of them identical configurations ... is the hardware identical? Compare outputs of lsusb and lspci as far as networking and wireless devices are concerned.

[SteveRiley]

Then I tried to boot the 7 vm, but I got a VMware unrecoverable error: Unexpected signal: 11.

Edit the VM config and change the number of CPU cores you've allocated to the guest. If 1, switch to 2. If 2, switch to 1. Then start the VM. Wait until Windows finishes booting, then do a proper shutdown. Now return the CPU core allocation to whatever it was before.

I recently noticed this problem on my Windows 7 VM that I've had for about a year; a hint in the log file led me to the discovery that changing the core allocation removed the unrecoverable error. Then, the other day, VMware finally blew its last chunk: I could reliably crash my entire machine with (1) VMware running, (2) in a call on SFLphone, and (3) simply dragging a window around on the desktop. I'm now running Windows 8.1 Update 1 in VirtualBox.

[Don]

Well, I "fixed" the problem, as long as one is not too careful about what "fix" means. I rolled my system back to 12.04, and everything works fine--wired and wireless. It's not elegant, but it gets my machine back in working order before I leave on a trip on which I need the machine. Apparently I'm not the only one experiencing wireless difficulties with 14.04. (One of the first things I noticed was that the ability to scan for wireless networks, so useful in 12.04, is either not available or only available somewhere other than Network Settings.) I think I'll wait a while before trying to upgrade to 14.04 again.
My profound thanks to all who offered help.