Upgrade to 1.10 failing

Topics: Administration, Installing Orchard
Feb 26 at 8:25 AM
Edited Feb 26 at 8:26 AM
I have tried upgrading a site from 1.9.0 to 1.10 using the "In-place" method described here http://docs.orchardproject.net/Documentation/Upgrading-a-site-to-a-new-version-of-Orchard and this download: https://github.com/OrchardCMS/Orchard/releases/download/1.10/Orchard.Web.1.10.zip
but trying to access the sites once all the new files are in place give huge traffic into the logs, and no responses from the page (just hourglass). I've tried all the usual recycling of app pool etc. The logs contain entries like:
2016-02-24 23:24:45,483 [784] Orchard.Environment.DefaultAssemblyLoader - (null) - Error loading assembly 'System.Data.DataSetExtensions' [(null)]
System.IO.FileNotFoundException: Could not load file or assembly 'System.Data.DataSetExtensions' or one of its dependencies. The system cannot find the file specified.
File name: 'System.Data.DataSetExtensions'
... and (more fully this time)...
2016-02-24 23:25:07,716 [784] Orchard.Environment.Extensions.Compilers.DefaultExtensionCompiler - (null) - Assembly reference 'System.Data.DataSetExtensions' for project '/Modules/Orchard.Scripting/Orchard.Scripting.csproj' cannot be loaded [(null)]
2016-02-24 23:25:07,732 [784] Orchard.Environment.DefaultAssemblyLoader - (null) - Error loading assembly 'Orchard.Scripting' [(null)]
System.IO.FileNotFoundException: Could not load file or assembly 'Orchard.Scripting' or one of its dependencies. The system cannot find the file specified.
File name: 'Orchard.Scripting'
at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection)
at System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.Load(String assemblyString)
at Orchard.Environment.DefaultAssemblyLoader.LoadWorker(String shortName, String fullName) in z:\TeamCityAgent\work\9f6cd39ff0f68f41\src\Orchard\Environment\IAssemblyLoader.cs:line 61
at Orchard.Environment.DefaultAssemblyLoader.<>c__DisplayClass4.<Load>b__2(String shortName) in z:\TeamCityAgent\work\9f6cd39ff0f68f41\src\Orchard\Environment\IAssemblyLoader.cs:line 28
at System.Collections.Concurrent.ConcurrentDictionary2.GetOrAdd(TKey key, Func2 valueFactory)
at Orchard.Environment.DefaultAssemblyLoader.Load(String assemblyName) in z:\TeamCityAgent\work\9f6cd39ff0f68f41\src\Orchard\Environment\IAssemblyLoader.cs:line 28

My environment is Server 2012, SQL 2012 Express, ASP.Net hosting with Arvixe.

My site works fine again when I clear /bin and /dependencies and replace all the old files, fortunately.

I have tried with both the new web.config as supplied and with a modified version of my previous one - made no difference.

Perhaps not relevant, but the only thing wrong with my site before the upgrade was that it refused to recognize the installed indexing module; I see "You need to enable an index implementation module like Lucene." in the dashboard no matter what I do with the "Indexing", "Lucene" and "Search" modules. I was hoping the upgrade would resolve this.

I have ensured that my app pool account has generous permissions on the site folders and files.

Any ideas why I might be getting these "Could not load file or assembly" errors and what I can try next? Should I upgrade to 1.9.3 first?