We had the same problem, this was resolved as below.
When we installed Altiris 6.9 SP4 we created and used a domain level service account (Altiris Service)
All of our images and desktop clients have the (Altiris Service) account in their local administrator group.
The (Altiris Service) account also has the appropriate access levels to all installation and image sources.
Because we are a multi site topology, allowing files to be copied using the Deployment server is extremely low, so we have configured all jobs to or "Copy Directly from source then Execute" and used the altiris service account credentials.
This has the effect on Windows 7 of executing the applicaiton install (or any other task) in the context of the Altiris Service Account user ID. thus it will have local administrative rights on the target machine.
I can then log in tot he client machine using hte Altiris Service account, and any windows will be avaliable, including desktop interaction requests.