SQL 2008 Cluster setup needs to be run twice (on a two node cluster) So you will end with two binaries install, one per node. This is different from SQL 2005 where it was just one setup that runs over the network, but prone to issues in case of missing dlls or stuff not properly copied (actually happened to me one time, long time ago, ugly experience detected almost a year later)

For that reason, I believe you need to fail over the passive node, become active, and run

SELECT @@VERSION