Netalyzer reporting "unable to send fragmented UDP traffic" after updating to 376.48

[Soylent]

I recently updated to Merlin 376.48 on an N66U, and ICSI Netalyzer has a new warning message:

Basic UDP access is available.
The client was unable to send fragmented UDP traffic. The most likely cause is an error in your network's firewall configuration or NAT.
The maximum packet successfully sent was 1472 bytes of payload.
The client was able to receive fragmented UDP traffic.

I did some searches but I can't find any information on how this affects my connection. My MTU is set as 1500 in the router.

What does it mean that I can receive but not send fragmented UDP traffic?

 

[RMerlin]

Try disabling NAT acceleration, could be a compatibility issue caused by it.

No idea what it concretely means.