Hi!
I have similar problem.
About month ago, when I updated to 2.0.1. version I have got situations, when pfsense freeezees.
Pfsense is installed on old HP E800 series server with PIII 1ghz CPU, 512Mb RAM and 17Gb SCSI hdd.
Firstly I though, that it is from bad RAM or HDD, but after changing them, everything continues.
I setted up another hardware, simple pc with 1,7Ghz Celeron Intel CPU, 768Mb RAM and 40Gb hdd.
Two days everything was ok, but then in one day it stops 3 TIMES!!
Then I thought, that it has got something common with ACPI, even I have got UPS.
Turned off ACPI support in pfsense.
Few days everything was OK after turning of ACPI in pfsense, but this night again it stops.
And I am a little bit desperate.
If hardware change doesn't help, it could be MBUFs?
Right now it is = 0.
In pfsense first page it shows 518/24896 MBUFs usage.
Any Ideas?