Running version 2.6.0. After about 3 weeks of boot time, pFsense would lose connectivity. Requests to the internet would fail and the pfSense GUI web interface was unreachable. The console displayed a repeated error swap_pager_getswapspace(x): failed. The dmesg log contained a list of errors for several services that were terminated (dhcpd, dnsmaasq, mpd5, nginx, php) with error message: pid xxxxx (service), jid x, uid y, was killed: out of swap space. In some cases you can use the top -o res -a command to sort by memory usage and find that bzip2 is consuming all resources.
The solution was to disable log compression under Status->System Logs-> Settings -> Log Compression -> then change to None.