Yes, the conversion from SQL Ce is probably the cause because SQL CE it did not include webstore. But the error says the webstore tables already exist. If you ran the scripts for those manually it may be missing a row in the mp_SchemaVersion table so it thinks it needs to run those scripts again and is trying to create things that already exist.
If Webstore is functional prior to the upgrade you may need to create or update a row in that table to contain:
webstore as the application name, you can put d0f50c83-9752-4722-8b0b-4bd9718966ff for the application guid and set Major, Minor, Build, Revision to 0 0 7 3
Also SQL CE did not support the [dbo] owner prefix on tables, but if that were causing problems I would expect errors with the core upgrade scripts.
Hope that helps,
Joe