What operating system are you using?
"Log on as different user" You mean you log onto the computer as a different user, correct? (As opposed to opening filemaker and entering a different password.)
If so, then the steps for this depend on you operating system.
I am running windows XP SP3. When i login to my PC as a different user and run filemaker, it comes up very quickly , but when i login back to the 'originial' user's account. Filemaker takes atleast 3 mins to come up