Description of problem:
Unfortunately, I was away from my PC for a few minutes {whilst letting it download the whole image sequence from the player for XKCD 'Time' ;-) http://geekwagon.net/projects/xkcd1190/}

I expected that Kde wouldl have gone into blank screen mode.

When I returned, and wiggled mouse and pressed keys to awaken from blank screen -screens would not respond.

PC still seemed to be running, just no video so I switched it off and on.

When I logged back in to KDE desktop - this null pointer error was there in the crash notifier.
 


Additional info:
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<ffffffffa00d52ac>] radeon_pm_set_clocks+0xbc/0x580 [radeon]
PGD 1afdd8067 PUD 1b3eae067 PMD 0 
Oops: 0000 [#1] SMP 
Modules linked in: fuse ip6table_filter ip6_tables ebtable_nat ebtables ipt_MASQUERADE iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack xt_CHECKSUM iptable_mangle tun bridge stp llc lockd bnep bluetooth sunrpc rfkill be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i cxgb3 mdio libcxgbi ib_iser rdma_cm ib_addr iw_cm ib_cm ib_sa ib_mad ib_core lm63 iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi hwmon_vid snd_hda_codec_hdmi snd_hda_codec_analog snd_hda_intel snd_hda_codec tuner_simple tuner_types snd_bt87x snd_hwdep snd_seq tuner snd_seq_device snd_pcm tvaudio acpi_cpufreq snd_page_alloc tda7432 mperf kvm_amd kvm snd_timer msp3400 nv_tco snd bttv btcx_risc tveeprom videobuf_dma_sg videobuf_core rc_core v4l2_common videodev media edac_core ppdev edac_mce_amd microcode forcedeth parport_pc parport soundcore pata_jmicron i2c_nforce2 asus_atk0110 k10temp uinput ata_generic firewire_ohci firewire_core crc_itu_t pata_acpi
sata_nv pata_amd usb_storage radeon i2c_algo_bit drm_kms_helper ttm drm i2c_core
CPU 2 
Pid: 888, comm: X Not tainted 3.9.10-100.fc17.x86_64 #1 System manufacturer System Product Name/M2N-SLI DELUXE
RIP: 0010:[<ffffffffa00d52ac>]  [<ffffffffa00d52ac>] radeon_pm_set_clocks+0xbc/0x580 [radeon]
RSP: 0018:ffff8801a35e9bd8  EFLAGS: 00010282
RAX: ffff8801b204d0c0 RBX: ffff8801b28f31b0 RCX: 0000000000000000
RDX: 00000000001ae5f0 RSI: 00000000001ae5ef RDI: ffff8801b28f26c0
RBP: ffff8801a35e9c58 R08: ffff8801b3449d48 R09: 0000000000000080
R10: ffffffff81ce0a20 R11: 0000000000000000 R12: ffff8801b28f2d10
R13: 0000000000000000 R14: ffff8801b28f3180 R15: ffff8801b28f2000
FS:  00007f10b89dd8c0(0000) GS:ffff8801bfd00000(0000) knlGS:00000000f76ea6c0
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000001b5d7e000 CR4: 00000000000007e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process X (pid: 888, threadinfo ffff8801a35e8000, task ffff8801afc70f20)
Stack:
 ffffffff811af880 dead000000100100 dead000000200200 ffff8801b121c040
 ffff8801b5590500 00000000000000db 0000000000000000 ffff8801a35e9ac8
 ffffffff811af880 dead000000100100 dead000000200200 ffff8801b28f2000
Call Trace:
 [<ffffffff811af880>] ? __pollwait+0xf0/0xf0
 [<ffffffff811af880>] ? __pollwait+0xf0/0xf0
 [<ffffffffa00867b0>] ? radeon_get_shared_nondp_ppll+0x100/0x100 [radeon]
 [<ffffffffa00d6400>] radeon_pm_compute_clocks+0xd0/0x220 [radeon]
 [<ffffffffa00867eb>] atombios_crtc_dpms+0x3b/0x120 [radeon]
 [<ffffffffa0056a62>] drm_helper_connector_dpms+0x72/0x130 [drm_kms_helper]
 [<ffffffffa0025c6d>] drm_mode_obj_set_property_ioctl+0x31d/0x330 [drm]
 [<ffffffffa0025cb0>] drm_mode_connector_property_set_ioctl+0x30/0x40 [drm]
 [<ffffffffa00144b3>] drm_ioctl+0x4d3/0x580 [drm]
 [<ffffffffa0025c80>] ? drm_mode_obj_set_property_ioctl+0x330/0x330 [drm]
 [<ffffffff814b490c>] ? input_event_to_user+0x5c/0x90
 [<ffffffff811aea67>] do_vfs_ioctl+0x97/0x580
 [<ffffffff8129e66a>] ? inode_has_perm.isra.32.constprop.62+0x2a/0x30
 [<ffffffff8129fcf7>] ? file_has_perm+0x97/0xb0
 [<ffffffff810dcfec>] ? __audit_syscall_exit+0x20c/0x2c0
 [<ffffffff811aefe1>] sys_ioctl+0x91/0xb0
 [<ffffffff81664377>] ? int_check_syscall_exit_work+0x34/0x3d
 [<ffffffff816640d9>] system_call_fastpath+0x16/0x1b
Code: 8b 2f eb 12 0f 1f 00 4d 39 ee 49 8b 45 00 4c 89 ef 74 24 49 89 c5 83 bf c4 00 00 00 02 75 e8 48 83 c7 48 e8 37 73 f9 ff 4d 39 ee <49> 8b 45 00 4c 89 ef 75 df 0f 1f 00 41 80 bf b0 10 00 00 00 74 
RIP  [<ffffffffa00d52ac>] radeon_pm_set_clocks+0xbc/0x580 [radeon]
 RSP <ffff8801a35e9bd8>