hh.exe problem in switch user

Hi there,

Anyone out there who could help me in this. So far, I can't get clearer
info/docs regarding this one; I would be more than grateful...

I have an app (impersonated from a service - SYSTEM account) that uses .chm
for help topics. Launching the chm file using HtmlHelp API somehow fails when
you're SYSTEM account so I changed it using hh.exe, CreateProcessAsUser and
WTSQueryUserToken. This works fine in both admin and limited user account
during normal logon. However, during user switching, limited user can't
somehow launch the chm file.

(SYSTEM account)
logon admin (from startup) -> launch chm file : ok
logon limited (from startup) -> launch chm file : ok
logon admin (from startup) -> switch user (limited) -> launch chm : nothing
happens
logon limited (from startup) - switch user (admin) -> launch chm : ok

No messages/warnings from windows event logs. Also, the API's are returning
nonzero (success), both WTSQueryUserToken and CreateProcessAsUser.

Though, this is not really a big issue but client is asking for explanations
and I can't get straightforward docs online.

Working with XP Prof SP3 and VC++ 6.0. Only happening in XP and Server 2003.
Everything works fine with Vista and Server 2008.