Odd error to display once Outlook opens but it appears that there may be an issue with the Outlook add-in. [The error is normally "LANDesk Antivirus unable to load the antivirus scan engine. Error- 2147024809 (0880070057)"]
Have you already tried disabling the Outlook add-in? If this does not resolve the issue you can try reinstalling just the AV before reinstalling the entire agent. To remove the AV open a command prompt and browse to "\Program Files\LANDesk\LDClient" and run "vulscan.exe /removeav". I recommend rebooting before reinstalling. Return to the same folder using command prompt and run "vulscan.exe /installav".
If this still does not resolve the issue, I once resolved a add-in issue by just replacing the dll from a working computer. I did this after reinstalling the AV and agent and for some strange reason this resolved the issue. The dll is "LDOutlAddin.dll" under " \Program Files\LANDesk\LDClient\Antivirus"