Hi!
Bittex support don't respond to the ticket. Apparently U market will be removed tomorrow. Withdraw your funds from Bittrex.
Trading is possible on C-CEX. I'll write tomorrow to Yobit support about issue with wallet. I have plans for the spring, I hope to be able to return to Bittrex.
P.S.: UWallet for Android will be updated on the weekends.
Yes, something strange is happening with Bittrex. Their support was much more responsive before, and they were active on Bitcointalk as well. Now I can see Ritche from Bittrex (richiela;
https://bitcointalk.org/index.php?action=profile;u=96390) has posted last time on October last year!!!
They seem to be having problems, and this behavior is unacceptable. I am starting to afraid they can go Cryptsy...

As to Yobit, you have no chance to get any reply from them. You can try though, maybe you are lucky, but they tend to ignore everyone except their own trolls and pumpers.
It would be nice to list UCoin on some additional exchange of medium size, like Cryptopia.no.nz, Alcurex.com or Bleutrade.com. Other options could also be goo. Too many exchanges are not needed, but 2-3 is just ok...