Did you change of Matlab version ?
I just did it with R2014a
testmatrix = rand(50,400);
save('test.txt','testmatrix','-ascii')
and i got a text file such as
7.9333239e-03 7.2173747e-01 5.0775133e-01 7.7271278e-01 1.4579592e-01 7.6052624e-01 1.7149844e-02 1.2863135e-01 3.1398573e-01 7.4287948e-01 1.9866456e-01 6.9662297e-01 3.8364462e-01 6.5203224e-02 6.7058812e-01 4.6045824e-01 4.0180554e-01 3.5262205e-01 5.6614612e-01 7.7905297e-01 7.5873115e-01 7.7782343e-01 7.5305231e-01 5.0488754e-01 8.4238319e-01 2.8728398e-01 9.5399787e-02 6.4921268e-01 2.4375847e-01 8.7876870e-01
...
this works just fine .
