I read that POS is insecure, does anyone know exactly what that means and does that apply to all POS coins including Mintcoin and ECC?
There are, in fact, two aspects of "coin security" as far as PoS coins like mintcoins, peercoins, or this one here are concenred:
PoS coins are only insecure if handled insecurely, this is not much different from any other Crypto coin (including PoW coins such as bitcoins or litecoins) out there. That perceived risk comes from the necessity to have one's coins in an unlocked "hot" wallet every now and then in order to do the "minting" and hence get the proof-of-stake reward or "interest". It does not mean that coins would have to be held in hot wallets all the time though. In order to receive "interest" of 20% p. a. for Minctoin or, say, 25% p. a. for Eccoin here, coins can be stored in secure cold storage (paper wallets, cold machines or the like) most of the time and only need to be moved to an unlocked hot wallet for minting after a certain period of time (over 20 days for Mintcoin, more than 42 days for Eccoin here). For the rest of the time, and while in secure cold storage, there will not be any additional risk of cracking or the like for your coins.
The other aspect is broader systems security of the entire coin infrastructure. This is actually better for PoS coins than "normal" coins based on PoW only as PoS coins are not vulnerable to attacks of 51% OF HASHING POWER but would require greater than 51% of MINTING VOLUME for a common "51% attack" to succeed. This fact greatly disincentivises any such attack on a PoS coin as potential attackers would have to acquire 51% of all coins in question at great financial cost first -- only to "throw it away" by destroying the coin they hold by their very act. This is, in fact, one of the (several) reasons for PoS to exist: increased overall Crypto coin systems security.
