"Improper store into indexable object" and weird variable names

Hi!

It happened that variables of my methods changed to t1, t2, t3, etc etc (see here: http://imgur.com/ptbmzMH ) and when I try to see the versions of a method, pharo shows "Improper store into indexable object" (see here: http://imgur.com/pwWT0yc ).

Can you help me, please? I'm on Pharo2.0, Latest update: #20619

Cheers
 Davide