sikuli script does not run from task schedular from windows after locking computer

I use a Windows 7 Enterprise 32 bit system in my job.In a project I have to connect to a web site and get some files from that site.Then I prepared a sikuli script that works fine from IDE and command line when I run it manually.It also worked fine when I add it to task scheduler while I logged into Windows and windows is not locked.But I have to use this script on every day morning at 07:00 and at that time my system is locked as I am not working.So script is not working when I put it into task schedule with the option "run the task if user is logged in or not" with password or without password.The script opens a firefox window,connect to a site,find and filter some data,export this data to excel and close the windows.
I will be very happy if you can help me about this problem.