>>Is this problem when you click on the Profile to get messages? I got a long delay there today.
>
>This is the query to get the online and offline users. The delay is caused by the search engine. We are offloading the search engine to another server this weekend. So, whenever a hit will be done on the search, it will not affect the Web site.
>
I just thought about something. Say, you're running this query and at the same time someone logs in or logs out. This may cause a deadlock if you're trying to update your tables at the same time, I think. Perhaps NOLOCK suggestion is really good for you.

>>In SQL Server 2008 you can use date field, but I don't know if this is going to solve the problem. You can use DATETIMEOFFSET as well.
>
>I am not sure what you recommend here. Could you elaborate a little bit more?

You were claiming that datetime field may be the issue. In SQL Server 2008 you can check

http://www.databasejournal.com/features/mssql/article.php/3718086/New-datetime-datatypes-in-SQL-Server-2008.htm