In QlikView Server 9 you can choose to run the distribution service with an x86 or x64 engine. If you have problems finding the right ODBC driver you can always modify your QlikView Server installation from "Add/Remove" program and change the engine (expand DistributionService). You will find this information in the QVS9 manual as well. Just bear in mind that it has t be one or the other, not both.
I tried this. I installed QVS 64 bit SR2 and chose to run the 32 bit for the Distribution Service. However i still can't get my qvw to reload. If i reload the qvw using QV 32 bit application instead of the QVS, it reloads just fine. But reloaded through the QVS, it just fails. The log (turned on logging in the qvw) doesn't say anything useful.
We change the version from 64 to 32, because on our server we have a Microsoft 32 bit Server installed. The fact is when you have a MS 32 bit, you should have a QV 32 bit installed. If you have a MS 64 bit, then install the QV 64 bit. The performance shouldn't change.