honestly I don't remember how i resolved, but there's a little trick to fix this problem: the problem itself is that when you switch user in the same console session then the system doesn't reload the right configuration file...
oh yes, found it (i think): search in your home directory for a file called ".bashrc". If it doesn't exist create it, open it and write something like
"source /etc/profile" without the "
and save. It should do the trick.
A little explanation (at my best effort, maybe i'm wrong): when you open a new console bash reads /etc/profile and some other personal config files. If you change user in the same console you will lose the configuration read before (for obvious reasons... ) but it doesn't reload anything. Except for a file named .bashrc
this should be quite true, i'm not sure it will resolve your problem, just give a try
if anyone has a better explanation is welcome... i hope i'm right...