I've been running a trial with untangle for the past week, and twice so far I've run into this scenario.
Running untangle in bridge mode between my router (m0n0) and the switches. I'm running in on a lenovo desktop using onboard plus a realtek pci card. Desktop has an 80 gig sata drive, 1 gb ram, dual core athlon 2.0 ghz. It will work fine for several days, and all of a sudden it will just stop passing any data. I'm able to get into the web interface on untangle with no problems, and it's responsive. Console is responsive as well. Ram isn't maxed (though I do experience some RAM creep the longer the box is up), and CPU is sitting at 0. 70ish gigs free on the hard drive too.
I've got about 30 users on it, running the entire open source package plus ad blocker, though I have firewall turned off. Page count on the web filter when it hung was about 130000 pages filtered.
Can anyone give me any ideas or things to try to keep it from hanging like this? I'd also like to know if the ram usage will just keep going up and up. It starts at about 450 megs of ram used, and after 4 days (my longest uptime without an issue) is about 750 used. Is it just going to keep going up, or is there a ceiling somewhere?