I am getting the exact same error message. All my units (Waveman) are working like they should in TelldusCenter (2.0.2 r1), but the scheduler refuses to work. I've tried running the application as an administrator and with XP SP2 compatibility mode, but I get the same error message no matter what. I'm running this in Win7 Ultimate x64 with all updates installed. It works fine on a Fujitsu Siemens Amilo xi1546 laptop running WinXP SP3. This leads me to believe that there might be a difference in the schedulig engines between the different versions, or that the devs didn't intend for us to use scheduling on modern systems.