Matthew,
Thanks for the sample output and the diagnostic report.
Your QRecallHelper process is indeed stuck and I vaguely remember this problem.
It would appear that QRecall is encountering an I/O error from the volume containing the archive:
2011-10-26 10:13:23.675 +0100 Details archive I/O error
2011-10-26 10:13:23.675 +0100 Details Cause: <IO> cannot read hash entry { API=FSReadFork, Pos=620910680, OSErr=-36, Length=12, File='/Volumes/My Book 1/Current Work Backup.quanta/hash.index', Class=CarbonFile }
There's a bug in 1.1.4 that when this kind of error happens, an internal dead-lock occurs and the process gets stuck.
So I suspect that you're having random problems reading/writing to your external drive.
First, make sure there's nothing wrong with external drive's volume format. Use Disk Utility to repair the volume.
Then make sure the QRecall archive is in good shape by running a Repair on the archive. I would also highly recommend that you schedule verify, merge, and compact actions to run on a regular basis. At that very least, schedule a verify to run once a week. This will alert you to any possible data integrity problems that might have crept into your archive.
This could, ultimately, be a hardware problem with the external drive. Once you've done these repair steps, we can revisit the problem in more detail should it reoccur.