I have a dual-core laptop with 2 gigs of RAM and Blender 2.62 running on linux ubuntu 12.04…
I am trying to model Barad-dur from LOTR and I was pretty sure that I could do it, but with just modelling a “simple” guard-tower with 334548 vertices, blender internal crashes even if the quality is putted in 10% with no Ray-tracing! Cycles renderer can’t build BVH, although it can preview it in render mode, Yafray crashes as well, LuxRender does’t even open and in all the cases the system lugs…
And it’s really strange, because when I used Kubuntu I rendered a project bigger than the one I am talking about and it was done in 1-2 hours with no system lugs…
What I am doing wrong?
Is it because of the hardware?
Or because of Ubuntu?
Or is it a bug of blender?
Or something else?
HELP!!!
Elaborate “crashes” - this is like calling the emergency saying “someone’s hurt, please come” 
First guess: 32b version -> runs out of memory.
Well, the fact that I can’t render it kind of hurts, really…
And why I can’t render the specific one and not other projects with the same complexity?
To repeat myself:
What error message, what’s blenders console output, what`s happening? when during rendering?
Do you mean I have to run Blender from the terminal and see what I get when I render?
Well, if that’s so, I have this:
Calloc returns null: len=16384 in tangent table, total 1957570552
Segmentation fault (core dumped)
Nono. You can enable blenders console under “Help”>“ToggleSystemConsole”.
All the intresting stuff for this topic goes there, unless there’s an error message.
Are you running 32bit OS + Blender?
Do you have a swap partition?
The alloc is defineately a memory related issue. Either you run out of memory, or your file has something in it to trigger a bug.
A signed integer has it’s positive maximum at 16384, so most likely you’re out of memory but I am not familiar enough with Blenders code base to interpret this error message.
The highly unlikely worst of cases is that one of your memory modules is faulty - but like I said usually the system freezes in this case and you don’t see any error - but I’ve heared of instances where a faulty memory module caused alloc problems.
Actually, the system “freezes” and I have to do everything in “slow motion”…
It doesn’t freeze completely but it responds VERY, VERY SLOWLY…
This sounds like your system is swapping on your hardisk and then it lags.
Close all windows (Browser, Filemanager, etc.), open a terminal > type top
You can see your memory and swap usage.
Open blender in another terminal and start with ./blender -d
Start your file and watch the top process in the other terminal.
You can try to start ubuntu without Unity, it cost mucho memory and slows a system down.
You can try Xubuntu, it is a light weight linux distri based on ubuntu.
A dual core laptop with 2 GB memory is slow. 
Cheers, mib.
Ok, problem solved…
Firstly, I ripped out Ubuntu and putted Bodhi Linux, which uses Enlightenment and is VERY lightweight…
Secondly, I searched the whole blend file to find what was going wrong and I found a subsurface modifier set to 4!
I immediately changed that to 1 and the render was finished in seconds in very high quality…
Thanks a lot for making me understand that it was a RAM problem…