Backing up Microsoft Sharepoint Services using Symantec Backup Exec is a common source of confusion.
For users of Backup Exec 11d, support for Microsoft Office Sharepoint Server 2007, and direct support for Sharepoint Services were introduced in June 2007 (see here). For users of earlier versions of Backup Exec it's not so clear-cut.
The confusion mainly stems not from Symantec, but from Microsoft. Microsoft produce Sharepoint Services, which you can find out more about by using the link above. Sharepoint Services is a free product. Microsoft also produce Microsoft Sharepoint Portal Server. Sharepoint Portal Server is not a free product. Its purpose is to provide a portal for one or more Sharepoint Services deployments.
Symantec provide an Agent for Sharepoint Portal Server. Using this agent you can backup a site collection where you have Sharepoint Portal Server installed. You can then do things like restore documents at a very granular level. The agent does not backup Sharepoint Services.
The common misunderstanding is for people to try to backup a Sharepoint Services site (where they don't have Sharepoint Portal Server) using the agent.
Without Sharepoint Portal Server, you have few options to backup Sharepoint Services. These are: