The subject behavior occurs because cluster processors must be all 32-bit or all 64-bit.

When you try to add a 64-bit node to a 32-bit cluster, you receive:

Computer:
Major Task ID:\{EBC8AEFF-10C3-4D5B-AC17-FC0F4C3871B7\}
Minor Task ID:\{2B3F3240-58AE-4F23-A4F8-70E620DABA7C\}
Progress (min, max, current):0, 1, 1
Description: Comparing processor architecture between the cluster and the nodes being added...
Status:0x8007170a
This computer cannot be made a member of a cluster.


Computer:
Major Task ID:\{2B3F3240-58AE-4F23-A4F8-70E620DABA7C\}
Minor Task ID:\{804DCF41-4734-4E84-8CF0-B7C3E4B8E2D6\}
Progress (min, max, current):0, 1, 1
Description: The node "" does not have the same processor architecture
             as the other nodes in the cluster and cannot be added to the cluster.
Status:0x8007170a
This computer cannot be made a member of a cluster.