Every kernel actually. ATI's "KMS", which is required by all X.org versions since Ubuntu 10.04, is simply broken for T60(I think it works for T60p though). The brokenness manifests itself as timer related messages, and Wi-Fi disconnects as you can see in the "dmesg" output below. Even when the wireless works it's unusably slow, e.g. max speed 1 Mbit/s or so. This is with kernel 4.2.3, but it's pretty much the same with all 2.6+ versions. As evidenced by the thread I linked above ATI/AMD can't be bothered to fix it. I don't think I will buy a laptop with anything other than Intel video in foreseeable future..

[  510.826637] perf interrupt took too long (2518 > 2495), lowering kernel.perf_event_max_sample_rate to 50100
[  606.665797] hrtimer: interrupt took 10982962 ns
[ 1013.906047] perf interrupt took too long (4994 > 4960), lowering kernel.perf_event_max_sample_rate to 25200
[ 1452.930290] CE: hpet increased min_delta_ns to 20115 nsec
[ 3494.345200] EXT4-fs (sda6): mounted filesystem with ordered data mode. Opts: (null)
[ 3623.503085] ieee80211 phy0: wls3: No probe response from AP <MAC> after 500ms, disconnecting.
[ 3623.558950] cfg80211: World regulatory domain updated:
[ 3623.558958] cfg80211:  DFS Master region: unset
[ 3623.558961] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp), (dfs_cac_time)
[ 3623.558966] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
[ 3623.558971] cfg80211:   (2457000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm), (N/A)
[ 3623.558975] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (N/A, 2000 mBm), (N/A)
[ 3623.558980] cfg80211:   (5170000 KHz - 5250000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (N/A)
[ 3623.558985] cfg80211:   (5250000 KHz - 5330000 KHz @ 80000 KHz, 160000 KHz AUTO), (N/A, 2000 mBm), (0 s)
[ 3623.558989] cfg80211:   (5490000 KHz - 5730000 KHz @ 160000 KHz), (N/A, 2000 mBm), (0 s)
[ 3623.558993] cfg80211:   (5735000 KHz - 5835000 KHz @ 80000 KHz), (N/A, 2000 mBm), (N/A)
[ 3623.558997] cfg80211:   (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 0 mBm), (N/A)
[ 3626.858218] wls3: authenticate with <MAC>
[ 3626.863050] wls3: send auth to <MAC> (try 1/3)
[ 3626.865514] wls3: authenticated
[ 3626.866167] iwl3945 0000:03:00.0 wls3: disabling HT/VHT due to WEP/TKIP use
[ 3626.866363] wls3: associate with <MAC> (try 1/3)
[ 3626.871222] wls3: RX AssocResp from <MAC> (capab=0x431 status=0 aid=1)
[ 3626.872483] wls3: associated
[ 3789.124688] CE: hpet increased min_delta_ns to 30172 nsec