Bind9 logging options

[Techi]

Hallo,
I have a problem in my recursive DNS servers (Bind 9, on RHEL 5). Intalled 
package on my system is the latest bind-9.3.6-4.P1.el5_4.2 from Red Hat. My 
problem is that sometimes, queries are failed with timeouts and that the one 
of my 2 DNS servers (the one set as primaryin my users) has 3 time more failed 
queries than the secondary, while the succesful queries are almost the same. . 
I am almost sure that the problem is network related (hardware or software), 
but I need a proof for that. Is there any way to log the timed-out queries in 
a log file? 

Thank you
Techi