Pptp server respond or wan or opt1 : with Loadbalancing features

[tutelacool]

Hi All,
I using the pfsense 1.2.2. Embedded image on Soekris net5501 version.
With the option "loadbalancing" . So all works perfectly :-).

The PPTP server mode is also active:

After reading on some forum, it seems that only the WAN interface is working and NOT the OPT1 (knowed bug probably resolved on version 2.0).
Believe it or not! The interface opt1 on my embeddedbox works to connect PPTP! So the both interfaces works…
BUT...  The box appears after X time to change the listening interface for the PPTP connection. That is to say that sometimes my connection on opt1 works and not on the WAN and sometimes the reverse.

If someone can possibly help me so that I only use the fixed WAN interface or opt1.
I already tried to set rules in the firewall. but nothing changes...