dial-up timeouts

[Vaclav Smidl <smidl@utia.cas.cz>]

Hi,
I have got a strange behaviour with ppp.
When I got connected, all programs using network (kmail,mozilla) suddenly
becomes very slow. They hangs for minutes without response.
When I shut down pppd, everything becomes normal.
I have a suspicion that it wait for some servise that is not avalilable
and it wait until timeouted.
The only application that is not affected is Konqueror - it works like a
charm.

I have no idea where to look. Can anybody recommend what logs to look
at?

Thanks in advance,

Vasek