virtualbox.org

Hello, everyone!
I have VirtualBox 4.2.12 installed on Windows XP and Ubuntu 11.10, as a guest.
I've allocated 1024MB of RAM for virtual machine and 10GB of hard disc space.
When I start the virtual machine, it runs normally. But then suddenly a crash occurs.
Guru Meditation Critical Error message occurs and offer me to stop the machine.
Those crashes may occur, when I'm doing something in terminal or doing nothing.
Can You help me to find out and fix that, please?
Thank You in advance.

00:00:06.708249 Host RAM: 1977MB total, 553MB available
00:00:07.380918 RamSize <integer> = 0x0000000040000000 (1 073 741 824, 1 024 MB)

Console: VM runtime error: fatal=false, errorID=HostMemoryLow message="Unable to allocate and lock memory. The virtual machine will be paused. Please close applications to free up memory or close the VM"

You need more RAM.