SQL Server will change the state of a database to suspect if it detects an event that compromises the integrity of the database. The database is completely unusable in this state. Your best course of action is to recover from the last known good backup.
In some rare cases, you may want to try to reset the suspect state of the database. For example, if SQL Server is unable to complete recovery on a database because the database or log is full. Please refer to Microsoft SQL Server Books Online for more details on how to perform this operation.