Been having an issue with certain users not appearing online or not seeing invitations from other users (on anetwork of around 50 users, we all use Windows Live to communicate within the business). For this certain guy, if I am signed into the desktop application I do not appear online to him. However if I sign into both the desktop app and then messenger online through hotmail, I appear online to him.

Have tried repairing Windows Live for both myself and him but still no luck.

Any ideas?