[Radiant] Big problem to install Radiant on Site 5

[Rails Italia]

Hi,
I tried to install Radiant 0.6.4 on Site 5 Hosting. The procedure has 
gone well and all the installation has completed. When I try to run the 
site (www.subdomain.mydomain.com) it shows the follow message:


    Application error

Rails application failed to start properly"
I didn't meet any trouble during installation.

Before installing I configured local gems on my account under 
/home/username/gems directory; I configured all required .gemrc and 
.bash_profile. Then I installed all gem required. I tried to run, by 
console, dispatch.fcgi, but the reponse is the same above.
I think that the problem is into .htaccess or into dispatch.fcgi ... I'm 
desperate developer.
Is there anyone can help me ? Is there anyone has an .htaccess that runs 
fine on Site5 hosting (under radiant ...) or/and dispatch.fcgi 
configuration that runs fine ?
Please help me ...
I appreciate also a serious and detailed tutorial to install radiant on 
site 5 (I think that all tutorials on the net (?) I verified ...).

Thanks

Carlo