12 Mbps internet connection downloading a 4.4 GB iso.

After totof's steps I have regular speed drops each 100 seconds aprox, but in effect no connection drops.

Speed takes aprox 30 seconds to achieve 12Mbps, so there is aprox 70 seconds of full speed before each drop.

On syslog I can see a periodic round of "Failed to get channel info for channel ..." messages each 120 seconds .

Log:
...
May  2 11:31:30 me kernel: [ 1276.388104] iwl3945 0000:0c:00.0: Failed to get channel info for channel 136 [0]
May  2 11:31:31 me kernel: [ 1276.812100] iwl3945 0000:0c:00.0: Failed to get channel info for channel 140 [0]
May  2 11:33:27 me kernel: [ 1392.612082] iwl3945 0000:0c:00.0: Failed to get channel info for channel 100 [0]
May  2 11:33:27 me kernel: [ 1393.036083] iwl3945 0000:0c:00.0: Failed to get channel info for channel 104 [0]
May  2 11:33:27 me kernel: [ 1393.464036] iwl3945 0000:0c:00.0: Failed to get channel info for channel 108 [0]
May  2 11:33:28 me kernel: [ 1393.888134] iwl3945 0000:0c:00.0: Failed to get channel info for channel 112 [0]
May  2 11:33:28 me kernel: [ 1394.312101] iwl3945 0000:0c:00.0: Failed to get channel info for channel 116 [0]
May  2 11:33:29 me kernel: [ 1394.736050] iwl3945 0000:0c:00.0: Failed to get channel info for channel 120 [0]
May  2 11:33:29 me kernel: [ 1395.163633] iwl3945 0000:0c:00.0: Failed to get channel info for channel 124 [0]
May  2 11:33:30 me kernel: [ 1395.592104] iwl3945 0000:0c:00.0: Failed to get channel info for channel 128 [0]
May  2 11:33:30 me kernel: [ 1396.016109] iwl3945 0000:0c:00.0: Failed to get channel info for channel 132 [0]
May  2 11:33:30 me kernel: [ 1396.440074] iwl3945 0000:0c:00.0: Failed to get channel info for channel 136 [0]
May  2 11:33:31 me kernel: [ 1396.864094] iwl3945 0000:0c:00.0: Failed to get channel info for channel 140 [0]
May  2 11:35:27 me kernel: [ 1512.568041] iwl3945 0000:0c:00.0: Failed to get channel info for channel 100 [0]
May  2 11:35:27 me kernel: [ 1512.996076] iwl3945 0000:0c:00.0: Failed to get channel info for channel 104 [0]
May  2 11:35:27 me kernel: [ 1513.421052] iwl3945 0000:0c:00.0: Failed to get channel info for channel 108 [0]
May  2 11:35:28 me kernel: [ 1513.845066] iwl3945 0000:0c:00.0: Failed to get channel info for channel 112 [0]
May  2 11:35:28 me kernel: [ 1514.273073] iwl3945 0000:0c:00.0: Failed to get channel info for channel 116 [0]
May  2 11:35:29 me kernel: [ 1514.696076] iwl3945 0000:0c:00.0: Failed to get channel info for channel 120 [0]
May  2 11:35:29 me kernel: [ 1515.120100] iwl3945 0000:0c:00.0: Failed to get channel info for channel 124 [0]
May  2 11:35:29 me kernel: [ 1515.545738] iwl3945 0000:0c:00.0: Failed to get channel info for channel 128 [0]
May  2 11:35:30 me kernel: [ 1515.973115] iwl3945 0000:0c:00.0: Failed to get channel info for channel 132 [0]
May  2 11:35:30 me kernel: [ 1516.397086] iwl3945 0000:0c:00.0: Failed to get channel info for channel 136 [0]
May  2 11:35:31 me kernel: [ 1516.821727] iwl3945 0000:0c:00.0: Failed to get channel info for channel 140 [0]
May  2 11:37:27 me kernel: [ 1632.572127] iwl3945 0000:0c:00.0: Failed to get channel info for channel 100 [0]
May  2 11:37:27 me kernel: [ 1632.997035] iwl3945 0000:0c:00.0: Failed to get channel info for channel 104 [0]
...