Testcase:
Connect two computers via the network. Work until you get a break prompt. 
Continue working.

Expected result:
Prompts disappear on both computers. No break windows appear.

Actual result:
Break window appears on the computer that is not currently in use


Alternative testcase:
Connect two computers via the network. Wait until you get a break prompt. Stop 
working. Wait until the break window appears. Continue moving the mouse or 
typing

Expected result:
User input is blocked. Timers in both break windows stop counting down at the 
same time.

Actual result:
The computer not currently in use continues counting down longer (though it 
eventually stops), resulting in unequal remaining break durations (and hence, 
the break windows are not removed simultaneously.

Fixed. Though it is still possible that both Workraves are slightly out of sync
(max about 2 seconds). Workrave processes its timer once every second. So both
workraves can be out of sync for 1s. Then there is some network delay... Every
30s the clocks are resync.