Field not found: 'Microsoft.CommerceServer.Catalog.Internal.Constants.CatalogResourceMajorVersion'

When accessing a Commerce Server 2007 site I get the exception below. This happened after I upgraded to SP2. I checked the Microsoft.CommerceServer.Catalog.dll in GAC and it seems to have this field. I tried to create a new test site on the same machine and get the same error.

Why is this error happening and how do I fix it?

[MissingFieldException: Field not found: 'Microsoft.CommerceServer.Catalog.Internal.Constants.CatalogResourceMajorVersion'.]
Microsoft.CommerceServer.Catalog.CatalogContext.InternalCreate(CatalogSiteAgent catalogSiteAgent, DebugContext debugContext, CacheConfiguration cacheConfiguration) +708
Microsoft.CommerceServer.Runtime.Catalog.CommerceCatalogModule.CreateCatalogContext() +293
Microsoft.CommerceServer.Runtime.Catalog.CommerceCatalogModule.get_CatalogContext() +138
Microsoft.CommerceServer.Runtime.Catalog.CommerceCatalogModule.OnBeginR开发者_开发问答equest(Object sender, EventArgs e) +24
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +171

See this blog for an answer. In short it's a SP2 problem.