Boot failure randomly. Can someone help?

I often get stuck at the boot on battery.

I can suspend and hibernate without any trouble (even on battery).

If I plug the energy cable everything goes right most of the time (edited June 13).

Adding "acpi=off" doesn't solve the issue.

Disabling power save from LAN at BIOS doesn't solve this too.

Memory test seems to be ok:

I can even compile a kernel without a problem:

Has someone a tip for this?
(I have the same questions marks in my mind as the image shows if not more :-/ )

obs.: this is an upgraded installation from Natty alpha.
edited I (May 22): I've installed a brand new final 11.04 and got the bug again.

edited II (June 13): I thought it was solved but it is not. After spending eight days off, the same problem happened even with the power cable connected. I had to reboot about 6 times until success.

edited III (June 14): I can boot (even with battery) if I disconnect the cable and take off the battery for a few seconds. This lead me to conclude that maybe something is kept into memory of some hardware. Maybe or maybe not related but I also have touchpad issues (jumps) with this machine.

edited IV (June 25): I opened gconf-editor and went to apps > gnome-power-manager and disabled everything possibly related to suspend or hibernate. No help.
Also I grabbed a Fedora live usb pendrive and got the same problem:

So I think it is a hardware problem related issue.

Solution 1:

Have a look inside log file viewer (press super and type "log file viewer") and see if you can find error messages prior to the bad_area_nosemaphore in your screenshot.

bad_area_nosemaphore: one of the causes for this can be faulty memory. That can also explain why you sometimes have a problem: if that bad memory is not touched everything works like a charm. If it does get touch unexpected results can be expected. In general: irregular behaviour during boot always start thinking memory 1st.

So run memtest from the live cd or from grub if you can boot into it and see if 1 of your memory modules is in bad shape and if so replace it.

Solution 2:

If this was from an alpha I would do a clean install, but that's my personal choice.

Having said which, looking at the evidence I would say that the kernel is probably trying to determine settings by probing interrupts or loading a module.

Try turning off the acpi in the grub boot parameters.