If you were starting a process from your desktop, that is owned by the Winlogon process, the application of SP1 prevents this behavior, as it closed this security loop hole.
If you need to be able to do this, run Regedt32 and navigate to:
On the Edit menu, Add Value name SecureDesktop, as a REG_DWORD data type. A data value of 0 implements the previous behavior. Any other data value, such as 1, or the deletion of the SecureDesktop value name, implements the new secure behavior.