Becoming utterly furious with this now.
3rd time i have had to re-sync the wallet (program). The gui totally freezes up and dies, upon re-start forces a re-sync (which i don't have the time to be cocking around with). luckily I've left all my coins in the poloniex exchange. If it happens again after yet another sync, the coins are just getting dumped back into the exchange. Gutted, as it looked promising......
Yes we are currently in transition from the heavyweight wallet to the lightwallet that will avoid those freezes. It is recommended to use the lightweight gui (if you use windows version there is another shortcut/ for universal use the lightweight *.bat).
Whenever you close the wallet without freezing a checkpoint is created so it is recommended to restart the wallet after a full sync.