Hello,
You want to use the same version of client as your server, so if your 
server is 7.2.1 then use that version for your 64 bit OS as i do.
Once you switch to 7.3.* you can then switch to 64 bit version of Networker 
client, with Windows 32 bit app as 7.2.1 are supported on 64 bit hardware.
So far i have not had any problems.

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