Mount-SPContentDatabase : Invalid column name 'HostHeader'

I am nearing the end (I hope) of a migration of sbs 2003 to sbs 2011. I've been following these steps:

http://technet.microsoft.com/en-us/library/gg563792.aspx#BKMK_DetachContentDb

Included in that document is this step:

Use the following command to mount your restored content database to Companyweb:

Mount-SPContentDatabase -Name "<DbName>ShareWebDb" –WebApplication http://companyweb<web-app-url>

The command I executed was:

Mount-SPContentDatabase -Name "ShareWebDb" -WebApplication http://companyweb

That resulted in the following error:

Mount-SPContentDatabase : Invalid column name 'HostHeader'.

At line:1 char:24

+ Mount-SPContentDatabase <<<<  -Name "ShareWebDb" -WebApplication http://companyweb

 + CategoryInfo          : InvalidData: (Microsoft.Share...ContentDatabase: SPCmdletMountContentDatabase)
[Mount-SPContentDatabase], SqlException

    + FullyQualifiedErrorId : Microsoft.SharePoint.PowerShell.SPCmdletMountContentDatabase

What did I do wrong here? (... and I thought I was so close to the end). The error message is cryptic it means nothing to me other than invalid data. 

Thanks, Mike