If you are experiencing unhandled exception errors occurring inconsistently, try:
delete the files (not subfolders) in the '/build/iPhone' folder, to force a full rebuild
run the app in Titanium Developer and ensure the console confirms that a full rebuild is taking place, then close the app as soon as it finishes loading-up
Open Xcode, navigate to the xcodeproj (checking the recency of the file date & time) and open it
From the "Build" menu, select "Run and debug - breakpoints on"
I have had occasions whereby running the app directly from Xcode does not produce unhandled exceptions that are encountered when running (incremental) builds directly from Titanium Developer.