Memory can be an issue with rootsPersona, sicne it keeps the entire GEDCOM in memory while processing it. The fact that FactDetail.php is listed is not significant, it was justthe lucky funion to be running when memeory ran out.
How much memeory PHP is allowed to use is defined in php.ini. You just need to bump yours up (I suspect is set to 64M).
While your in there,check all these settings:
memory_limit = 128M <-- just what I use, use your own discretion.
upload_max_filesize = 128M <-- how large is the GEDCOM?
max_execution_time = 60 <- probably set to 30, which is too low fro large GEDCOM processing
max_input_time = 60 <- I just keep it the same as mex_execution_time
I'm not sure how you are running your site, so not sure where to tell you to look for the php.ini file.