If you want to do it in a pretty brutish way you can do this
[cellData{300,1}] = [1:500]'; %initialize cellData
matrixedData = [cellData{:}]'; %gives you a 300X500
problem1mat1 = matrixedData(1:150,:);
problem1mat2 = matrixedData(151:300,:);
problem2 = {matrixedData};