Need help removing ruby

[Roger]

I installed ruby, rails, gem, rvm in ubuntu 11.10 and tried to update 
ruby from 1.8.7 to the recommended 1.9.2 and it fails.

No matter what I do rails reports /usr/bin/ruby1.8: bad interpreter:
ls -l /usr/bin/ruby*
lrwxrwxrwx 1 root root   22 2011-11-24 14:02 /usr/bin/ruby -> 
/etc/alternatives/ruby
-rwxr-xr-x 1 root root 5516 2011-07-28 07:24 /usr/bin/ruby1.9.1

  ls -l /usr/bin/gem*
lrwxrwxrwx 1 root root   21 2011-11-24 14:02 /usr/bin/gem -> 
/etc/alternatives/gem
-rwxr-xr-x 1 root root  545 2011-05-17 06:47 /usr/bin/gem1.8
-rwxr-xr-x 1 root root  547 2011-07-28 06:10 /usr/bin/gem1.9.1
lrwxrwxrwx 1 root root    8 2011-04-11 03:45 /usr/bin/gemtopbm -> gemtopnm
-rwxr-xr-x 1 root root 9572 2010-06-25 22:50 /usr/bin/gemtopnm


Synaptic says that 1.9.1 is 1.9.2 and this is confusing because 1.9.1 
has incompatibilities.

I have tried erasing and deleting all instances of ruby, rails, rvm and 
reinstalling with apt-get, with rvm, etc but am so stuck.

Googling has not helped, Ive been at it all day and no luck, how should 
this be solved please?
Many thanks in advance
Roger