I recently noticed that wireless performance on my built-in Intel Wireless WiFi Link 5100 dropped from adequate speeds both over local network (laptop->router) and over internet (laptop->router->speed test sites) down to hideously slow - less than 2mbps. The problem appears to be with using wireless N rather than wireless G.
Other PCs with wireless have no problem with the N wireless in the house. In fact, to get adequate speeds, I have to put the router in b/g only modes - if wireless N is available it auto-selects and bogs down horribly.

Once I move my new router or my old router to wireless G only, my speeds are consistently at where they should be, internet download-wise. However, this does limit me to 54mbps on the local network, with the typical interference issues wireless G experiences as well.
Not to mention the work wi-fi, which I don't have the option of changing bands with.

Now the gritty details necessary:

sudo lshw -C network:
Code:
 *-network               
       description: Wireless interface
       product: Wireless WiFi Link 5100
       vendor: Intel Corporation
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: wlan0
       version: 00
       serial: 00:16:ea:85:96:e2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=iwlagn ip=192.168.10.101 latency=0 multicast=yes wireless=IEEE 802.11abgn
       resources: irq:31 memory:fdffe000-fdffffff
Results from dmesg | grep iwl
Code:
[   17.430392] iwlagn: Intel(R) Wireless WiFi Link AGN driver for Linux, 1.3.27ks
[   17.430395] iwlagn: Copyright(c) 2003-2009 Intel Corporation
[   17.451335] iwlagn 0000:03:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
[   17.451366] iwlagn 0000:03:00.0: setting latency timer to 64
[   17.451458] iwlagn 0000:03:00.0: Detected Intel Wireless WiFi Link 5100AGN REV=0x54
[   17.505241] iwlagn 0000:03:00.0: Tunable channels: 13 802.11bg, 24 802.11a channels
[   17.505330] iwlagn 0000:03:00.0: irq 31 for MSI/MSI-X
[   17.762943] phy0: Selected rate control algorithm 'iwl-agn-rs'
[   17.772318] iwlagn 0000:03:00.0: firmware: requesting lbm-iwlwifi-5000-2.ucode
[   17.808056] iwlagn 0000:03:00.0: lbm-iwlwifi-5000-2.ucode firmware file req failed: -2
[   17.808061] iwlagn 0000:03:00.0: firmware: requesting lbm-iwlwifi-5000-1.ucode
[   17.905834] iwlagn 0000:03:00.0: Loaded firmware lbm-iwlwifi-5000-1.ucode, which is deprecated. Please use API v2 instead.
[   17.905840] iwlagn 0000:03:00.0: loaded firmware version 8.24.2.12
[   18.047744] Registered led device: iwl-phy0::radio
[   18.047766] Registered led device: iwl-phy0::assoc
[   18.047781] Registered led device: iwl-phy0::RX
[   18.047796] Registered led device: iwl-phy0::TX
Note: When I check /lib/firmware, iwlwifi-5000-2 firmware is present:
Code:
-rw-r--r--  1 root root 345K 2009-11-10 03:21 iwlwifi-5000-2.ucode
so I have no idea why the message "the bm-iwlwifi-5000-2.ucode firmware file req failed: -2" prints.

iwconfig results (when connected to wireless in 'B/G mixed' mode):
Code:
wlan0     IEEE 802.11abgn  ESSID:"Atheros"  
          Mode:Managed  Frequency:2.462 GHz  Access Point: 00:14:D1:69:2B:1E   
          Bit Rate=1 Mb/s   Tx-Power=15 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=70/70  Signal level=-24 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0
iwconfig results (when connected to wireless in 'N' mode)
Code:
wlan0     IEEE 802.11abgn  ESSID:"Atheros"  
          Mode:Managed  Frequency:2.462 GHz  Access Point: 00:14:D1:69:2B:1E   
          Bit Rate=0 kb/s   Tx-Power=15 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=70/70  Signal level=-23 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0
I have noted that the 'Bit Rate' settings are fairly frequently low or incorrect. For 802.11g it seems to be more often correct than 802.11n, however.

ifconfig (wireless N mode)
Code:
wlan0     Link encap:Ethernet  HWaddr 00:16:ea:85:96:e2  
          inet addr:192.168.10.101  Bcast:192.168.10.255  Mask:255.255.255.0
          inet6 addr: fe80::216:eaff:fe85:96e2/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:65895 errors:0 dropped:0 overruns:0 frame:0
          TX packets:48047 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:80796868 (80.7 MB)  TX bytes:23654321 (23.6 MB)
ifconfig (wireless b/g mixed mode)
Code:
wlan0     Link encap:Ethernet  HWaddr 00:16:ea:85:96:e2  
          inet addr:192.168.10.101  Bcast:192.168.10.255  Mask:255.255.255.0
          inet6 addr: fe80::216:eaff:fe85:96e2/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:65913 errors:0 dropped:0 overruns:0 frame:0
          TX packets:48079 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:80798994 (80.7 MB)  TX bytes:23660010 (23.6 MB)
Any thoughts or help would be greatly appreciated - this wireless N bug is irking, since I'd like to start stream from my main PC to my laptop for VLC to do music, TV shows, etc rather than running constant maintenance cleanups on my laptop to have enough HDD space.

Thank you!