How can I troubleshoot why Ubuntu keeps crashing on my laptop?

How can I troubleshoot why Ubuntu keeps crashing on my laptop?

I have a one year old Acer Aspire 4752G netbook running Kubuntu 12.04 LTS with all the latest distribution updates installed.
It was previously running great until about a week ago when it suddenly started crashing repeatedly.
Previously, on the rare occasion that it froze completely, even though I couldn't Ctrl+Alt+F1 to a console, the Alt+SysRq+r (eisub) was able to close everything down relatively gracefully and restart, but now, even Att+SysRq does nothing when it freezes.
The last crash occurred at around 10:40am today (May 26) (log time).
How can a I begin troubleshooting this?
These are the higlights I've identified from various logs.
dmesg.log
[    0.069749] CPU0: Intel(R) Core(TM) i3-2350M CPU @ 2.30GHz stepping 07
[    0.176277] Performance Events: PEBS fmt1+, SandyBridge events, Intel PMU driver.
[    0.176282] PEBS disabled due to CPU errata.
[    0.176285] ... version:                3
[    0.176286] ... bit width:              48
[    0.176287] ... generic registers:      4
[    0.176289] ... value mask:             0000ffffffffffff
[    0.176290] ... max period:             000000007fffffff
[    0.176291] ... fixed-purpose events:   3
[    0.176293] ... event mask:             000000070000000f
[    0.729751] HEST: Table not found.
[    0.729754] PCI: Using host bridge windows from ACPI; if necessary, use "pci=nocrs" and report a bug
[    0.730025] \_SB_.PCI0:_OSC invalid UUID
[    0.903601] ACPI: Deprecated procfs I/F for battery is loaded, please retry with CONFIG_ACPI_PROCFS_POWER cleared
[    3.152702] ACPI Warning: For \_SB_.PCI0.PEG0.PEGP._DOD: Return type mismatch - found Integer, expected Package (20110623/nspredef-1060)
[    3.152702] ACPI Warning: For \_SB_.PCI0.PEG0.PEGP._DOD: Return type mismatch - found Integer, expected Package (20110623/nspredef-1060)
[    3.152709] ACPI Exception: AE_OK, Invalid _DOD data (20110623/video-1175)
[    3.155864] acpi device:2f: registered as cooling_device4
[   27.635581] wl: module license 'MIXED/Proprietary' taints kernel.
[   27.635587] Disabling lock debugging due to kernel taint
[   27.928424] input: Acer WMI hotkeys as /devices/virtual/input/input7
[   27.929470] acer_wmi: Get 0x1 Device Status failed: 0xe2 - 0x0
[   27.929796] acer_wmi: Get 0x800 Device Status failed: 0xe2 - 0x0
[   27.930105] acer_wmi: Get Current Device Status failed: 0xe2 - 0x0
[   28.496068] acer_wmi: Get Current Device Status failed: 0xe2 - 0x0
The following are errors from syslog:
May 25 12:52:28 peter-aspire-ubuntu kernel: [ 4428.392128] [drm:gen6_sanitize_pm] *ERROR* Power management discrepancy: GEN6_RP_INTERRUPT_LIMITS expected 17000000, was 12060000
May 25 13:03:26 peter-aspire-ubuntu kernel: [    0.000000] ACPI: IRQ0 used by override.
May 25 13:03:26 peter-aspire-ubuntu kernel: [    0.000000] ACPI: IRQ2 used by override.
May 25 13:03:26 peter-aspire-ubuntu kernel: [    0.000000] ACPI: IRQ9 used by override.
May 25 13:03:26 peter-aspire-ubuntu kernel: [    0.176282] PEBS disabled due to CPU errata.
May 25 13:03:26 peter-aspire-ubuntu kernel: [    0.724077] ACPI: Using IOAPIC for interrupt routing
May 25 13:03:26 peter-aspire-ubuntu kernel: [    0.764035] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT]
May 25 13:03:26 peter