If you "kill" the client (which one ever) you will lose at max (unless there is a bug) the currently processed workunit. You can configure the client to write a checkpoint file though. Just change the corresponding value in the config file (config.txt?). It is set to 180 (seconds) IIRC, I you have a stable computer runing 24/7 you should increase that value .... on systems that get switched on and off (notebooks, etc) I would let it at 180 ...

Wirthi