On our development box SD application server (Windows 2003 Server) I applied SP22 for test purposes and then needed to revert back to SP18. I uninstalled all the apps (server, client, and agent) and then reinstalled and applied SP18. The problem is that the database version is at v4.50588.2205 and the application server is at v4.5.0588.1805. So, I can't start the application server. Is there away to "downgrade" the database server or do I need to have them restore my database from last weeks backup to bring it back to the correct version?
You can't downgrade an SP. That is because each SP does some structure changes to the database so the previous versions can't use an upgraded db. The only option is to restore your database from the last backup while is SP18.