This is usually caused by a null value in the RUN registry keys.
From JSI:
1. Edit: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer. If the right hand pane has an entry NoSaveSettings that is a 1, set it to zero until the problem is resolved. This should be a REG_BINARY value.
2. Edit: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
For each Value, make sure that the string is valid, i.e., if the Value is ActiveMovie File Extensions, the string of this REG_SZ entry should be ActMovie.exe /Check and not null. The string must always start with an executable file. If it doesn't, fix it or delete the Value.
Other keys to check are:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServices
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
John