SQL Job datetime comparison problem

Hi, my problem is the following.

I have a stored procedure that runs the following t-sql:

delete MYTABLE
where DATETIMECOLUMN < dateadd(day,-29,getdate())

If I run this from Query Analizer with EXEC, it works fine.

When I run this as a scheduled job it deletes all rows where the date is AFTER dateadd(day,-29,getdate()), which is wrong. The strange thing is, the same scheduled job run on another server works fine.

I know Server Agent stores some of its dates in another format. But is this related, ¿why does it work in the other server?

Any help appreciated.
Cristian

Actually the problem is really this:

1. I open query analizer and connect to a DB server on another IP in the same network.

2. I execute the following statements on a table that has a clustered index (descending) on the column that appears in the where clauses.

select * from MYTABLE
where DATETIMEFIELD < dateadd(day,-29,getdate())

delete MYTABLE
where DATETIMEFIELD < dateadd(day,-29,getdate())

3. The funny thing is, the above commands do not affect the same rows!

4. If I take away the index, the both commands affect the same rows.

5. The same work fine on another server (with the index).

Thanks for any comments.
Cristian