>>Yesterday evening I configured OpenVPN on my box with a client link to
>>one of my friends. Maybe that is problem?
> 
> 
> Might have something to do with it.  I know out of mbuf can also be
> caused by bugs of some sort, or other issues, but am not familiar
> enough with the kernel internals to know just what..

Well, I will do a bit of more testing on the weekend when I can monitor 
the box closely.
Then I can provide more netstat stats and so on.

I also found some filter on my WAN interface not to work, but thats 
another issue.
I should also look at the stable version I think...