I am not completely familiar with what RVM does, but the command proceeds to install to a directory under usr/share/ruby-rvm, and copy gems. JRuby does not do these things.
We do not issue error message such as
ERROR: Cannot switch to 1.6.2 for this interpreter.
If the user is getting permission errors, there are directories or files with insufficient privileges for the user who's running it.
If execv is getting EPERM, the chances are, there is a file without execute permission which something (and I am guessing it is a shell script via RVM) is trying to run.