Just wanted to give you all who offered some advice a little update. I never fully got this to work, but I did find some problems with the last thing I posted.
I changed the file that I was reading from to a .dat, cause one of my classmates suggested that our SDK (version 1.5, I think?) did not like .txt files. I do not know how true this is, have not managed to confirm or disprove this theory. I moved the file reading code out of the "MortCalc()" method, since that was not allowing the file read to occur until that method was called. I put it into the end of the MikesCalc() method. I put in a System.out.println temporarily, just to verify that both of my arrays were receiving the information. That part works. I also got rid of one of the array initializations under the class, and put it in the method that was using it.
I ran out of time for the assignment, so I had to turn it in as is. I still want to figure this out, though. Another person suggested that I was initializing one of my arrays in such a way that it was causing it to fill the JComboBox with an empty string. This may be the case, but I do not know how to fix it. If anyone is interested in providing a few more pointers, I will provide any info they want. Thanks for your time.