Unfortunately I saw this too late. I just posted the below in another blog, but it better belongs here:

I have a problem with the new withdraw function at bittrex.

The new withdraw window is very confusing. Here it is:

It seems to be impossible to withdraw steem from Bittrex to a steemit account. If you enter a steemit name with less than 10 characters you get an error message as below. You can’t proceed. If your steemit name is less than 10 characters, then you can’t withdraw.

If you choose a steemit name of more than 10 characters, you still can’t enter the 6-digit authentification code.

You are blocked completely at that point. (Tested on an iPad).