This can occur if VirtualBox is running on FreeBSD:

You have plenty of ram left and try to copy a large file.

Suddenly, and at random points, the copy will abort, i.e. with a message like "write failed" and a memory error.

 

 

Adjust your virtualbox settings in /boot/loader.conf to have this setting for netgraph:

# for vbox
vboxdrv_load="YES"
net.graph.maxdata=65536

 

 

Source:

 

http://lists.freebsd.org/pipermail/freebsd-stable/2011-July/063322.html

 

The person who originally asked about this problem wanted to get a warning into the port but was ignored.

I hope the wiki article will help some people find the solution faster.