Hi Andrew,
please review Posting code? Read this first! .
The cause of the crash is similar (or same?) as before: it’s a bug in your program, unrelated to ROOT, in the handling of some strings. You can step through with a debugger to see what’s happening (see link above for a tutorial) or run the program within valgrind --suppressions=$ROOTSYS/etc/valgrind-root.supp ./yourprogram to see if it sees something fishy going on (remember to compile the program with debug symbols (i.e. -g compilation flag).
Cheers,
Enrico