Crashing when attaching

When I first installed RefMan 12, it worked fine.  Now when I try to attach a PDF file to a citation I get the message:

The instruction at “0X0047bf4c” referenced memory at “0xoe386d0c”.  The memory culd not be “read”.

Then I have to choose OK or Cancel, both of which crash the program to the WIndows desktop.  I used Memtest86 to aggressively check my memory, and it encountered no errors so I don’t think this is a hardware issue (the problem is unique to Ref Man).  I tried to fix this by rerunning the installer in “Repair” mode but that didn’t fix it either.

Sometimes when this happens I get another message right before it closes:

Unknown software exception (0Xc0150019) occurred in the application at location 0X7c9449cf.

This doesn’t happen if I open up each citation and then attach, but this slows me down and is rather tedious.  Is there something I can do?