Hello Petr!
I use slow dial-up GPRS Internet connection. Usually DXCluster works fine when I choose one of a REAL DX Cluster. Problems are with REVERSEBEACON, especially during contest. In some minutes after start DXCluster window hangs up. Reconnecting to REVERSEBEACON has no effect, connecting to another  DX Cluster fails too. Disconnecting & connecting occurs but there are no spots. The only way to get spots is to reload CQRLog itself and to connect to DX Cluster again.
I couldn't upload a screenshot. If it needs, I'll send by e-mail.
CQRLog v 1.5.2, Slackware 12 system.
73!   Andrey