Explorer.exe Annoyance

[SisAdMan]

I'm a sys admin on the servers where I work and I'm having a problem. We run a Standard Desktop image as our operating system, Windows XP with a special little bar on the top. That's the only difference besides software restrictions and security policies. Now I have a user who's client isn't loading explorer.exe on startup. Any ideas? I've checked the reg, the shells are there. Anyone know anything short of a reload to correct this, it'd be a big help. thanks