VS2008 binary 3x times slower than VS2005?

I've just upgraded a native C++ project from VS2005-SP1 to VS2008-SP1
The first thing I tested was a very basic functionality test of the application and the first thing I noticed is that the main number-crunching algorithm performs three times slower in the VS2008 binary.
I tested again the VS2005 binary to make sure there isn't any other difference and it still performed as it did before.
Did anyone stumble into this?

From stackoverflow

• Strangest. Thing. Ever.

  It seems that the project upgrade wizard of vs2008 simply doesn't copy the 'Optimization="2"' property so the new project is left with no optimization in release.

  The fix was to go to the properties dialog, change optimization to 1 and then back to 2. compile again and everything works it should.

  I couldn't find any official reference for this only this obscure reference in an MSDN forum.

  Drew Hoskins : It's nice to know the optimizer is kicking that much butt, at least.