Symptoms
A stored procedure that excecutes in a timely fashion ( from 10 to 30 seconds ) in SSMS takes up to 15min or hangs on Reporting Services or Visual Studio 2005.
Tried in my case
I made sure to use the same parameters and the same security context on both. cutting and pasting the stored procedure body doesn't work, due to some inner complexity that is best left encapsulated.
Workaround
What seems to work, is to create the dataset anew in the faulty report, but it feels too much like waving a dead chicken in front of the computer to be fully satisfactory.
If anyone has an explanation, i'll take it.