I work for an OEM that uses a Windows XP system to control a piece of
manufacturing equipment. During system setup we change the default system
shell (HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell) to
our user interface application (A .NET 2.0 Application)

When customers logon to the system with a new account (i.e. a new user, one
that has never been used), 1 out of about 10 times the "Personalized
Settings" window appears (upper left corner of the screen) and stops at
Internet Explorer. In some cases we've waited upto 2 hours, and the shell
never starts. We primarily have IE6 installed, but in atleast one case we've
had IE7, it also happened more often with SP2. The equipment has to be power
cycled to recover from the problem.

Has anyone else seen this? Anyone have any ideas about how we can debug
this?