Could not load file or assembly while performing database upgrade

The database fails to update and the Database update results page show:

Could not load file or assembly 'Microsoft.SqlServer.BatchParser, Version=10.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91' or one of its dependencies. The system cannot find the file specified.

This is probably because the SMO assembly for SQL server is 32bit and the IIS system is 64bit.  

To resolve, in the IIS Advance setting for the Application pool set 'Enable 32=bit Applications' to true.