>I have a weird situation. During our test phase, from a test environment which is practically the same as the production, everything went ok. We have this SQL, which has always executed in a flash. Basically, the SQL select is instant. So, during all of our tests, we never saw anything wrong in there as it immediately executes. However, once we moved that to production, the same SQL select takes between two and five minutes. As I said, the data load is pratically the same. Anyone would be able to suggest what could be a factor here?

Never forget the obvious: check the hardware...
we had a flaky disk/controller coupling, where internal error reset the hardware interface to use PIO although both support UDMA.
WindoZe is extremely helpful because it tries to minimze errors and does NOT tell you about such a reset :-(((
You only feel it as disc actions are crawling if not coming from cache...
Or the disk itself might be on the brink of desaster, rereading sectors until they are correct.

regards

thomas