For 1) please gather the McScript.log and Agent_<machine>.log from the Agent data folder for the machine - this will help determine if the task actually was attempted and what happened at tha time. The default location for Agent Data folder is Documents and Settings\All users\Application Data\McAfee\Common Framework. These logs should be under the DB subfolder of the agent data folder.
2) Please post this as a separate query in the VSE forum.
3) What version /build of ePO are you using? Please gather what changes (if any were made) other than the Agent Extension upgrade on the ePO server. Also, gather the DB\logs\server.log file from the ePO server.