[EpiData-list] want help

I use EpiData 3.1. In one of my projects I encountered a strange problem: The qes file contains 78 variables in total. Among them there are about 50 Y/N(1/0) variables.  When I enter data into the rec file by EpiData and enter a series of "N"(0) for these Y/N variables ,the EpiData begins producing a prompting frame showing : "Access violation at addrss 00000000. Read of address 00000000." I have to hit the "OK" button repeatedly to make the prompting frames disappear. After they disappear, the program in chk file seems having stopped working. How can I enter my data normally?