User Profiles Missing

In one week I had two users who logged on in the morning as they usually do with the same user name as always. However, when they logged on their user profiles were blank. They had none of the customized Icons that are normally on their screen, their network paths were missing along with some MS-Excel spreadsheets. Also, Excel and Word came up as if it were just installed and not configured yet. I had just installed the latest Virus protection software from Norton just days before and so I do not think it is a Virus problem unless it is a very new Virus. Any Ideas?

THanks
Randy Nix