Bind slowdown

Hello,

Just today I noticed huge Bind (DNS) query slowdown, nothing has been
changed.
Actually this is strange because if i use dig it shows reasonable query
response time (~100, then if cached a few ms), but to query the DNS i
have to wait a couple of seconds.

Example:
me$ dig somehost.com

(here i wait a few seconds)
[...]
;; Query time: 110 msec
[...]

Again:
me$ dig somehost.com

(no delay)
[...]
;; Query time: 14 msec
[...]

Also the clients using the same DNS server have complained.
The same effect is if any other program tries to resolve a host, if it's
a internet browser then first it says the host could not be resolved and
as the page's been cached on next refresh the page is loaded.

Nothing has been changed (configuration etc. no zones have been added, no
new clients have pointed their computers to this DNS). What could cause
such a delay?
The connection from me or from the clients to the DNS is from 3ms to
100ms.


P.Krumins