Getting an "System.Exception" error when trying to change the data type of a column from date to (4335661)

Getting an System.Exception error when trying to change the data type of a column from date to datetime with the alter table option.
See complete error message below:

System.Exception
Error on extended region.
Message : Ungültiger Objektname sysproperties.
Stack Trace:
bei Quest.Compare.Schema.MSSQL.DBModel.Loader.CNSSysDatabase.FillDataSet()
bei Quest.Compare.Schema.MSSQL.DBModel.Loader.CNSSysDatabase.FillDataBase()
bei Quest.Compare.Schema.MSSQL.DBModel.WrapServer.CreateDB(ICNSServer iServer)
bei Quest.Compare.Schema.MSSQL.Scripter.CNSMSScripter.FillRootNode(Int32 index1)
bei Quest.Toad.SqlServer.Doe.CNSScripting.CNSScripter.LoadObjects()
bei Quest.Toad.SqlServer.Doe.Tables.TableProperties.get_Scripter()
bei Quest.Toad.SqlServer.Doe.Tables.TableProperties.getAlterSQL(Nullable`1 useExAlter)
bei Quest.Toad.SqlServer.Doe.Tables.TableProperties.GetScript(Nullable`1 useExAlter)

Using SQL Server 2008.

Steps to reproduce the problem:

1] Go to Object Explorer
2] Select a table
3] r-click and select Alter table
4] Select a date column and change the data type to datetime

Wrong compatibility level .
The database is SQL Server 2008 and the compatibility level is 90(which belongs to SQL server 2005).
When upgrading databases from an older version of SQL Server using either the backup and restore method or detach and attach method the compatibility level does not automatically change and therefore your databases still act as though they are running using an earlier version of SQL Server. From an overall standpoint this is not a major problem, but there are certain features that you will not be able to take advantage of unless your database compatibly level is changed.

Pleasechange your database compatibly level to 100. (For SQL Server 2008 the correct compatibility level is 100).