I don’t do this usually, but this time this is really interesting.
I want to recommend a very good blog post written by Kenneth Van Surksum about troubleshooting Task Sequences in Configuration Manager. Find it here http://www.techlog.org/archive/2009/03/01/troubleshooting_task_sequences.
He talks about the smsts.log file, where to find it during installation and what tool you can use to read the logs easily. Also, at the end, he wrote a list of helpful links to get you start troubleshooting.
Definitely I will add his feed to my “SCCM blogs I read” list.