Piling on.
Backwards restores are not possible. When you create/restore a database on a newer version of SQL Server, it uses all the new functions storage mechanisms, etc., that define the new version of SQL Server. The older versions can't read that stuff.
Solution is as John has already outlined.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning