I also ever experienced this problem. This problem occured probably, you use username and password to log on to your computer, so sql server need to verify the user who authorized to use the sql server service.. But sometimes sql server cannot redirect to the account, so we need to configure the user.
Here's the step :
1. open sql server configuration mangager
2. choose sql server 2005 services
3. right click sql server integration services, choose properties
4. choose log on tab, select this account, enter your username and password which is used to log on your computer.
5. reopen the business intelligence studio. There you are, the data flow task component can work properly again.
finally, i found out how to solve this problem...
thanks to sulton..