Sebastian,
SOLVED! It was not due to the portallocalization table, but to wrong entries in web.config.
Looks like the upgrade package (I upgraded this host to 7.2.1) did not modify some entries: comparing my web.config to the one of a newly installed 7.2.1, I found I had to manually change
<add name="CorePermissionProvider" type="DotNetNuke.Security.Permissions.CorePermissionProvider, DotNetNuke.Provider.CorePermissionProvider" providerPath="~\Providers\PermissionProviders\CorePermissionProvider\" />
to
<add name="CorePermissionProvider" type="DotNetNuke.Security.Permissions.CorePermissionProvider, DotNetNuke" providerPath="~\Providers\PermissionProviders\CorePermissionProvider\" />
I also did the same for the following entries:
<add name="ModuleIndexProvider" type="DotNetNuke.Services.Search.ModuleIndexer, DotNetNuke.Search.Index" providerPath="~\Providers\SearchProviders\ModuleIndexer\" />
changed to
<add name="ModuleIndexProvider" type="DotNetNuke.Services.Search.ModuleIndexer, DotNetNuke" providerPath="~\Providers\SearchProviders\ModuleIndexer\" />
<add name="SearchDataStoreProvider" type="DotNetNuke.Services.Search.SearchDataStore, DotNetNuke.Search.DataStore" providerPath="~\Providers\SearchProviders\SearchDataStore\" />
changed to
<add name="SearchDataStoreProvider" type="DotNetNuke.Services.Search.SearchDataStore, DotNetNuke" providerPath="~\Providers\SearchProviders\SearchDataStore\" />
<add name="FileModuleCachingProvider" type="DotNetNuke.Services.ModuleCache.FileProvider, DotNetNuke.Provider.ModuleCaching.FileProvider" providerPath="~\Providers\ModuleCachingProviders\FileModuleCachingProvider\" />
changed to
<add name="FileModuleCachingProvider" type="DotNetNuke.Services.ModuleCache.FileProvider, DotNetNuke" providerPath="~\Providers\ModuleCachingProviders\FileModuleCachingProvider\" />
<add name="MemoryModuleCachingProvider" type="DotNetNuke.Services.ModuleCache.MemoryProvider, DotNetNuke.Provider.ModuleCaching.MemoryProvider" providerPath="~\Providers\ModuleCachingProviders\MemoryModuleCachingProvider\" />
changed to
<add name="MemoryModuleCachingProvider" type="DotNetNuke.Services.ModuleCache.MemoryProvider, DotNetNuke" providerPath="~\Providers\ModuleCachingProviders\MemoryModuleCachingProvider\" />
Hope this helps,
al.