I make it a hard rule to immediately verify to the highest (regular) level before depositing a thing. I think quite a few of these situations would be avoided if everyone did that. Not all, but surely some. Even if you've truly done nothing wrong, something has triggered this and now your stuck trying to do something you could have done well before putting your hard earned money on the table. Don't you think there's at least a chance you'd better off if you'd verified first? Anyway, unless you've deposited so much money that an exchange which makes a million a day would be tempted to steal it, it's almost certainly an erroneous system trigger. Not a ploy to take what is probably small fry to them. Annoying, but not a scam.
This is good advice, but in reality its not practical when you need to pick up a trade on something and don't have time to wait days/weeks to get verified before the price goes up.
When I created my account, even non-verified basic accounts could still withdraw. That changed 3 days after I joined. Interestingly, the newer your account the less you can withdraw. I can currently withdraw 0 BTC.
Regardless, doing enhanced verification was the very first thing I did. I'm not doing any shady, and using all my real info so why should I worry about being rejected or being stuck in hell? Bittrex is meant to be a reputable exchange. Through no fault of my own I was screwed by a policy change days after joining, along with a buggy verification process. They deserve to be called out until they improve their service.