Performance Center 9.5 : Cannot run the Load Test. Unable to retrieve available project's timeslots

I installed Performance Center 9.5 and configured it in windows 2003 with SQL server 2005.
Whene I tray to do a trial loadtest after configurat it, I get this error :
" Cannot run the Load Test. Unable to retrieve available project's timeslots "

And in the Event Log i found this message :
" Mar-2010 4:19:59 PM Unable to get project available timeslots. Error cause is - -2147467259| -2147467259 /loadtest/ Run Start.asp -> [module] w3wp [file] orchidtimeslot.cpp [line] 2162 Error "

Thank you.