Hi

I have the same problem. I still see the wireless networks. Sometimes connecting to the network  is possible but transfering datas is near to impossible once the "fail to flush all tx fifo queues" happens.

$ lshw ouput
    description: Laptop
    product: 900X3C/900X3D/900X4C/900X4D (System SKUNumber)
    vendor: SAMSUNG ELECTRONICS CO., LTD.
Its a Samsung New Series 9 900X

Wlan chip is a
           *-network
                description: Wireless interface
                product: Centrino Advanced-N 6235
                vendor: Intel Corporation
                physical id: 0
                bus info: pci@0000:01:00.0
                logical name: wlan0
                version: 24
                serial: c8:f7:33:19:7e:f4
                width: 64 bits
                clock: 33MHz
                capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
                configuration: broadcast=yes driver=iwlwifi driverversion=3.13.0-32-generic firmware=18.168.6.1 ip=172.19.3.235 latency=0 link=yes multicast=yes wireless=IEEE 802.11abg
                resources: irq:49 memory:f0600000-f0601fff


$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.1 LTS"

outpt of dmesg:
[13562.125715] iwlwifi 0000:01:00.0: fail to flush all tx fifo queues Q 2
[13562.125731] iwlwifi 0000:01:00.0: Current SW read_ptr 138 write_ptr 140
[13562.125827] iwl data: 00000000: 00 0c 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[13562.125893] iwlwifi 0000:01:00.0: FH TRBs(0) = 0x00000000
[13562.125957] iwlwifi 0000:01:00.0: FH TRBs(1) = 0x8010208b
[13562.126022] iwlwifi 0000:01:00.0: FH TRBs(2) = 0x00000000
[13562.126087] iwlwifi 0000:01:00.0: FH TRBs(3) = 0x803000c7
[13562.126152] iwlwifi 0000:01:00.0: FH TRBs(4) = 0x00000000
[13562.126215] iwlwifi 0000:01:00.0: FH TRBs(5) = 0x00000000
[13562.126279] iwlwifi 0000:01:00.0: FH TRBs(6) = 0x00000000
[13562.126342] iwlwifi 0000:01:00.0: FH TRBs(7) = 0x007090a3
[13562.126527] iwlwifi 0000:01:00.0: Q 0 is active and mapped to fifo 3 ra_tid 0x0000 [200,200]
[13562.126710] iwlwifi 0000:01:00.0: Q 1 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[13562.126911] iwlwifi 0000:01:00.0: Q 2 is active and mapped to fifo 1 ra_tid 0x0000 [138,140]
[13562.127109] iwlwifi 0000:01:00.0: Q 3 is active and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.127291] iwlwifi 0000:01:00.0: Q 4 is active and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.127475] iwlwifi 0000:01:00.0: Q 5 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[13562.127675] iwlwifi 0000:01:00.0: Q 6 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[13562.127857] iwlwifi 0000:01:00.0: Q 7 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[13562.128033] iwlwifi 0000:01:00.0: Q 8 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[13562.128235] iwlwifi 0000:01:00.0: Q 9 is active and mapped to fifo 7 ra_tid 0x0000 [164,164]
[13562.128418] iwlwifi 0000:01:00.0: Q 10 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[13562.128600] iwlwifi 0000:01:00.0: Q 11 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.128782] iwlwifi 0000:01:00.0: Q 12 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.129014] iwlwifi 0000:01:00.0: Q 13 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.129226] iwlwifi 0000:01:00.0: Q 14 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.129409] iwlwifi 0000:01:00.0: Q 15 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.129591] iwlwifi 0000:01:00.0: Q 16 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.129842] iwlwifi 0000:01:00.0: Q 17 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.130026] iwlwifi 0000:01:00.0: Q 18 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13562.130207] iwlwifi 0000:01:00.0: Q 19 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.128576] iwlwifi 0000:01:00.0: fail to flush all tx fifo queues Q 2
[13565.128589] iwlwifi 0000:01:00.0: Current SW read_ptr 140 write_ptr 165
[13565.128679] iwl data: 00000000: 00 f0 ff 0f 00 00 00 00 00 00 00 00 00 00 00 00  ................
[13565.128738] iwlwifi 0000:01:00.0: FH TRBs(0) = 0x00000000
[13565.128799] iwlwifi 0000:01:00.0: FH TRBs(1) = 0x8010209b
[13565.128856] iwlwifi 0000:01:00.0: FH TRBs(2) = 0x00000000
[13565.128913] iwlwifi 0000:01:00.0: FH TRBs(3) = 0x803000c8
[13565.128973] iwlwifi 0000:01:00.0: FH TRBs(4) = 0x00000000
[13565.129034] iwlwifi 0000:01:00.0: FH TRBs(5) = 0x00000000
[13565.129096] iwlwifi 0000:01:00.0: FH TRBs(6) = 0x00000000
[13565.129153] iwlwifi 0000:01:00.0: FH TRBs(7) = 0x007090a3
[13565.129375] iwlwifi 0000:01:00.0: Q 0 is active and mapped to fifo 3 ra_tid 0x0000 [201,201]
[13565.129553] iwlwifi 0000:01:00.0: Q 1 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[13565.129731] iwlwifi 0000:01:00.0: Q 2 is active and mapped to fifo 1 ra_tid 0x0000 [140,165]
[13565.129909] iwlwifi 0000:01:00.0: Q 3 is active and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.130159] iwlwifi 0000:01:00.0: Q 4 is active and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.130413] iwlwifi 0000:01:00.0: Q 5 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[13565.130650] iwlwifi 0000:01:00.0: Q 6 is active and mapped to fifo 2 ra_tid 0x0000 [0,0]
[13565.130870] iwlwifi 0000:01:00.0: Q 7 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[13565.131052] iwlwifi 0000:01:00.0: Q 8 is active and mapped to fifo 4 ra_tid 0x0000 [0,0]
[13565.131233] iwlwifi 0000:01:00.0: Q 9 is active and mapped to fifo 7 ra_tid 0x0000 [164,164]
[13565.131432] iwlwifi 0000:01:00.0: Q 10 is active and mapped to fifo 5 ra_tid 0x0000 [0,0]
[13565.131606] iwlwifi 0000:01:00.0: Q 11 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.131778] iwlwifi 0000:01:00.0: Q 12 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.131951] iwlwifi 0000:01:00.0: Q 13 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.132121] iwlwifi 0000:01:00.0: Q 14 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.132293] iwlwifi 0000:01:00.0: Q 15 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.132464] iwlwifi 0000:01:00.0: Q 16 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.132677] iwlwifi 0000:01:00.0: Q 17 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.132839] iwlwifi 0000:01:00.0: Q 18 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13565.133010] iwlwifi 0000:01:00.0: Q 19 is inactive and mapped to fifo 0 ra_tid 0x0000 [0,0]
[13568.131478] iwlwifi 0000:01:00.0: fail to flush all tx fifo queues Q 2
[13568.131493] iwlwifi 0000:01:00.0: Current SW read_ptr 140 write_ptr 197
[13568.131607] iwl data: 00000000: 00 f0 ff 0f 00 00 00 00 00 00 00 00 00 00 00 00  ................
and so on