UDP traffic blocked by a floating tule

[sarbian]

I had a strange problem while trying to set up my QoS.
When I set up a pass floating rule involving DNS UDP traffic I can not do any dns request anymore. The same rule on any of the interface works fine.
If I enable logging on the rule the log is fine, all request on port 53 are allowed but any nslookup on the console time out. If I disable the rule it works again.
I tried with a "clean" config ( no trafic shapper ) and still have the problem as soon as I activate the floating rule.

LAN is a bridge with 3 interface and WAN is a single interface, the  System Tunables are set up as explained in the sticky subject. The build is the nanobsd of jul 23.

Config attached.

config-pfSense.localdomain-20100724193007.txt