Problem creating scheduled taks, Task Scheduler cannot create the task

Hi, I have a problem when creating a scheduled task in Windows Server 2008 R2 Standard x64 which is client of Windows Server 2003 SBS.

When I click finish on scheduled taks wizard the following message appears: Task Scheduler cannot create the task. The user account is unknown, the password is incorrect,or the account does not have permission to create the task.

I tried both local administrator and domain administrator with no success.

P.S. According to other forum I tried to install subinacl and run these three commands from a cmd.
cd\
cacls c:\windows\tasks /T /E /P Administrators:F
cacls c:\windows\tasks /T /E /P SYSTEM:F

These commands grant full permissions to the tasks folder for the user group Administrators and the user System.

After these commands the situation is the same as I described above.