Do you have your mouse inverted?
System > Configuration > Input > Mouse > Invert mouse
There is a cursor bug with this setting on. If it is your case I am afraid you can either disable the option or wait for a fix, unless someone discovered a workaround.
Edit: However I am unable to reproduce the problem I describe above so maybe it was fixed and you experience another issue.
Can you tell us your Ryzom client version? Is it from Apple store, steam or stand alone client?
(client versions are written on various places or you can use /version command in-game)
System > Configuration > Input > Mouse > Invert mouse
There is a cursor bug with this setting on. If it is your case I am afraid you can either disable the option or wait for a fix, unless someone discovered a workaround.
Edit: However I am unable to reproduce the problem I describe above so maybe it was fixed and you experience another issue.
Can you tell us your Ryzom client version? Is it from Apple store, steam or stand alone client?
(client versions are written on various places or you can use /version command in-game)