I can confirm this error. I have the following setup:
Site 1----------------------- Site 2
| |
DNS at 192.168.11.123 Site2:Static route to 192.168.11.123 via LAN interface (Goes through IPSec)
I get the same error "A valid gateway must be specified".
Running an older version of pfSense on other hardware does not have this issue.
Non-working version:
2.0-BETA4 (i386)
built on Mon Sep 27 05:13:14 EDT 2010
FreeBSD 8.1-RELEASE-p1
Working (old) version:
2.0-BETA4 (i386)
built on Sun Sep 5 18:43:23 EDT 2010
FreeBSD 8.1-RELEASE