zone transfers sticking on one port?

[Chris Fabri]

I'm seeing what I think is an odd behavior with named, and want to know if 
this is in fact how things should work.

We had blocked port 39999 on our border to help deal with the Beagle 
virus.  We found out eventually that this was causing slave transfers to 
from our nameserver to an off-site secondary to fail with the "failure 
trying master error...:timed out"

I actually did a sniff, and I could just see all these UDP requests going 
on on 39999 and not getting answered.   Other ports were obviously going 
through ok.

Why was named hanging up on this port?    Shouldn't it just brush this off 
and try another port >1023?     This doesn't make any sense to me.   chris