Our programs are written in VB and we currently use OO4O, however even though the VB portion works OO4O doesn't in 64bit. What is the least painful path to migrate to something that will work (without ditching VB, that's not an option at this time) in 64bit?
The least painful solution would be just to run the existing 32 bit app on the 64 bit OS. Install 32 bit Oracle client and you should be good to go.
As far as migration goes, ODP.NET is the migration path from OO4O, and supports 64 bit.
Hope it helps,