Select problems

Hi:

I've just migrated  from Linux/PostgreSQL 7.2 to
Windows/PostgreSQL 8.0.3. I have a large view. When I make:

"Select ..... WHERE mydate = 'anydate'"the view lasts 19 seconds to complete. But, when I make:
"Select ..... WHERE mydate >= 'anydate'"the view lasts 7 minutes.

With PostgreSQL 7.2 they both last for equal time.

I did a vacuum analyze with no success.

Please, could you help me?
Thanks in advance
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