Through Managed Software Delivery Policy deploy software but failed!

hi,

I have a All-in-One Altiris Notification Server 7.1 (Virtual Machine) for PC inventory & software deployment with MSSQL database 2008 R2.

1) I create a Managed Software Policy with a Managed Software to install (it's Ultra VNC)

2) However, when I enabled the policy. The client cannot install that software successfully.

- In the client log error message is found: "Failed to start SWD task: The system cannot find the file specified. (-2147024894) "

3) Hovever, I found the installer (.exe) is already downloaded and located in client's PC Path "C:\Program Files\Altiris\Altiris Agent\Agents\SoftwareManagement\Software Delivery\{697FAB65.........}\cache

Why cannot install it? Thanks