swap_pager: indefinite wait buffer:

I have a virtualbox VM of FreeBSD-CURRENT running on my work laptop which I’m using for testing & development. To bring the system up to date I started buildworld after updating src, going back to check on the build process I found my SSH session had hung and the VM console had starting showing swap_pager: indefinite wait buffer: followed by values for objects in buffer, block number & size.
A search on google brought up the following answer from UNIXguide

This means that a process is trying to page memory to disk, and the page attempt has hung trying to access the disk for more than 20 seconds. It might be caused by bad blocks on the disk drive, disk wiring, cables, or any other disk I/O-related hardware. If the drive itself is actually bad, you will also see disk errors in /var/log/messages and in the output of dmesg. Otherwise, check your cables and connections.

Increasing the amount of RAM allocated to a VM seems to resolves the issue without having to resort to checking virtual cables or connections.

Update 4/1/2013

It seems that I had forgotten to define MALLOC_PRODUCTION in /etc/make.conf as this problem was also raised on the FreeBSD/ARM mailing list