It happened to me several times with minor altcoins. The last one is Giftcoin. At one day the wallet just stops syncing. It got me puzzled, since as I know the whole cryptocoin system builds on p2p scheme. I have several connection, still the wallet is not syncing. What could be the reason? I am not asking this about a specific altcoin, but generally, what could cause a wallet not to sync for every user? Is there anything that can be done as an ordinary user to solve this problem?