I assume you have made your installations based on the standard installables.
Last year I had the same problem.
AFAIK the user and pasword for the windows setup and the ubuntu setup are different!
It is best to check the configuration file for the correct user and pasword to use.
Added later:
For the versions I used it was:
- Ubuntu: user= openerp
pasword=postgres
- Windows: user= openpg
pasword=openpgpwd
For connection with pgAdmin:
- Host: localhost
- Port: 5432 SSL blank
- Maintenance DB: postgres
If you try to make a remote connection you get standard a connection error. For security reasons this is not allowed. If you want to change this you need to change the configuration paramaters.
Can you post a screenshot of your error and the log of software?
It's not really an OpenERP question. You could look at http://dba.stackexchange.com and find that the question has been answered there.
@Lorenzo Cabrini: Link or it did not happen