Upgrade error from 1.1.5 to 2.0.5

[gh658804]

While upgrading from a working 1.1.5 to 2.0.5 (after i logged in and pressed "update database"), i received the following error. The user has permission in the DB (owner) and the folder structure (1.1.5 was working fine). Where should i start checking?

Unhandled com_exception: Source: Microsoft OLE DB Provider for SQL Server
Description: Cannot drop the trigger 'alerts_type_id_delete', because it does not exist or you do not have permission. in C:\inetpub\apps\WebIssues\v2.0\system\db\mssql\engine.inc.php on line 85
Stack trace:
#0 C:\inetpub\apps\WebIssues\v2.0\system\db\mssql\engine.inc.php(85): com->Execute()
#1 C:\inetpub\apps\WebIssues\v2.0\system\db\connection.inc.php(215): System_Db_Mssql_Engine->execute()
#2 C:\inetpub\apps\WebIssues\v2.0\system\db\connection.inc.php(186): System_Db_Connection->executeArgs()
#3 C:\inetpub\apps\WebIssues\v2.0\system\db\mssql\schemagenerator.inc.php(127): System_Db_Connection->execute()
#4 C:\inetpub\apps\WebIssues\v2.0\system\db\schemagenerator.inc.php(158): System_Db_Mssql_SchemaGenerator->executeAlterTable()
#5 C:\inetpub\apps\WebIssues\v2.0\setup\updater.inc.php(461): System_Db_SchemaGenerator->removeReferences()
#6 C:\inetpub\apps\WebIssues\v2.0\setup\update.php(149): Setup_Updater->updateDatabase()
#7 C:\inetpub\apps\WebIssues\v2.0\setup\update.php(132): Setup_Update->updateDatabase()
#8 C:\inetpub\apps\WebIssues\v2.0\setup\update.php(42): Setup_Update->processForm()
#9 C:\inetpub\apps\WebIssues\v2.0\system\web\component.inc.php(100): Setup_Update->execute()
#10 C:\inetpub\apps\WebIssues\v2.0\system\web\application.inc.php(77): System_Web_Component->run()
#11 C:\inetpub\apps\WebIssues\v2.0\system\core\application.inc.php(210): System_Web_Application->execute()
#12 C:\inetpub\apps\WebIssues\v2.0\system\bootstrap.inc.php(130): System_Core_Application->run()
#13 C:\inetpub\apps\WebIssues\v2.0\setup\update.php(180): System_Bootstrap::run()
#14 {main}