Why does data import so slowly on 2013b?

I upgraded from 2012b to 2013a and importing data from a .txt file now takes much longer than it used to. My data is composed of a one row header with the variable names (~100) and many rows (anywhere from 100,000 to 600,000) of corresponding numeric data. It took a few minutes to import before, but now takes 30 or 45 minutes (I haven't timed it yet to get an exact number). Does anyone know why the new release is so slow? Also, I have been using the Import window to import my data and I thought that using importdata() might be more efficient; however, I need my data in column vectors with variable names pulled from the header, and I could only manage to get a structure from importdata(). My experience with structures is very limited and I am afraid that I will make a syntax error while dealing with them that will skew or exclude part of my data in a way that is not easily detected. Any suggestions or work arounds? And again, why is the new version so much slower? Thanks.

P.s. Everything mentioned here has been done on the same machine with no significant changes of any kind other than the upgrade to 2013a and the addition of the statistics and image processing toolboxes (the data mentioned is not image related though). Also, I am not using any scripts or functions of my own during this process, it's all native to MATLAB.