Mike,
I have backup exec 10d running on a Windows 2000 Advance Server media server. I have installed Hot Fixes 1, 4, 6, 7, 8, 9, 10, and 13 (except for #1, they're the ones that show up when you search). On my x64 Windows Server 2003 computer running SQL Server 2000, I have installed the Hotfix 1, per Symantec's instructions, including the Advanced Open File Option, and I still cannot backup open sql databases.
Add me to the list of users looking for the CORRECT answer to this question. I specifically upgraded to 10d when a Symantec sales rep told me it was what I needed to backup my x64 Windows Server 2003, SQL 2000 database.