Could you be so kind as to state the major revision of LANDesk you use (8.7 or 8.8 I imagine) and what level of service pack you are on? This would help along.
Generally, one of the first things to do here, is to make sure you've got the latest AV-engine for your version of LANDesk.
There's no "general" problems I'm aware of (David would know better here) in regards to definition updates from clients that I am aware of - the first stop would be again here to make sure that the clients are up to date.
You can get the latest AV-related patch(es) for your specific version from LANDesk support, at a push (and this would be also standard procedure if/when you'd log this as a support incident).
I seem to - very distantly - remember some issue with Outlook 2007 (but that was 1-2 years ago and has long been fixed) ... that's about it from me.
- Paul Hoffmann
LANDesk EMEA Technical Lead