[Chimera-users] MD Trajectory Error

I'm trying to run a molecular dynamics simulation in Chimera 1.12rc on a small molecule. On the first run, it worked perfectly. On subsequent runs, when it begins the MD simulation it errors with the following message in the reply log: "The existing trajectory output files are not compatible with the current molecular system, and therefore cannot be appended to with additional MD steps. You need to either remove/rename the existing files, or specify different file names for output." I've tried to find the trajectory output files in /tmp, I've tried reinstalling Chimera, I've looked in other directories without any luck. What should I be doing at this step? Where can I find these files? Thanks! Bryan