I have just now downloaded the client from http://kent.dl.sourceforge.net/project/ryzom/ryzom_setup_644.exe and installed it. I can confirm the installer isn't broken. Are you using the chrome browser by chance? I noticed it tends to abort downloads from time to time, very odd behaviour.
The filesize was for my download as follows
arc
The filesize was for my download as follows
19.10.2015 19:56 1.501.611.693 ryzom_setup_644.exe
arc
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