I also get two different results. According to the BOL, OBJECTPROPERTY() is used to return information about object in the current database. This query:

>USE northwind
>SELECT *
>FROM pubs..sysobjects
>WHERE OBJECTPROPERTY(ID, N'IsUserTable') = 1

does not use it in that way. The current database is Northwind and you're trying to retrieve info about objects in pubs. OBJECTPROPETY does not appear to work in the context that you want to use it.

-Mike