Happened to me as well the other day. I think the problem is low Gas price setup in your wallet, but maybe it could be that the order is already filled.
I think it is not a Gas problem, as I experienced both before. If it was Gas you'll be getting this error "
Warning! Error encountered during contract execution [Out of gas]".
I got "
Warning! Error encountered during contract execution [Bad jump destination]" before when I was sending a token [
vSlice] out of MEW during the time that it was locked. In any way, does Equal token have lock period?