Will not run reports on one user

Will not run reports on one user

Something strange is happening with my CRM-- when running reports on leads, contacts etc, one user is not working on its own.
When I am running a report with all of the users, his records appear. If I run a report using criteria to remove all other users except for him his records appear. But, if I run a report using just his name as a criteria it tells me that there is no data.
My reports run just fine for everyone else, and I did not change any fields between his reports and theirs. Any idea what's going on?